Random Vibration Analysis of a - · PDF fileCSI ANSYS Tip of the Week Introduction What is a...
45
Random Vibration Analysis of a Circuit Board Sean Harvey August 2000 CSI Tip of the Week hvordan man velkommen foråret
Transcript of Random Vibration Analysis of a - · PDF fileCSI ANSYS Tip of the Week Introduction What is a...
Random Vibration Analysis of aCircuit Board
Sean Harvey
August 2000
CSI Tip of the Week
hvor
dan
man
vel
kom
men
foraring
ret
CSI ANSYS Tip of the Week
bull Outlinendash Introductionndash Sample Problem
bull Descriptionbull Pre Processing Steps Omittedbull Interactive steps
ndash Specify Modal Analysis
ndash Specify Modal AnalysisOptions
ndash Constrain Board
ndash Solve Modal
ndash Specify Spectrum Analysis
ndash Specify Analysis Options
ndash Specify PSD Settings
ndash Specify PSD vs Frequency
Random Vibrationsbull (Continued)
ndash Plot Input PSD
ndash Specify Damping
ndash Flag Nodes to get PSD Input
ndash Solve for Participation Factors
ndash Set PSD Calculation Controls
ndash Solve Random Vibration Solution
ndash Set Mode Combination
ndash Calculate mode combinations and 1sigma response
ndash Post Processing Results Summary
ndash 1 sigma Results
ndash Post Processing 1 sigmaDisplacements
ndash Post Processing 1 sigma Stresses
ndash Plotting Response PSD in Post 26
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis
bullA Random Vibration Analysis is a form of SpectrumAnalysis
bullThe spectrum is a graph of spectral value versusfrequency that captures the intensity and frequencycontent of time-history loadsbullRandom vibration analysis is probabilistic in naturebecause both input and output quantities representonly the probability that they take on certain values
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis(continued)
bullRandom Vibration Analysis uses Power spectral densityto quantify the loading
bull (PSD) is a statistical measure defined as the limitingmean-square value of a random variable It is used inrandom vibration analyses in which the instantaneousmagnitudes of the response can be specified only byprobability distribution functions that show theprobability of the magnitude taking a particular value
CSI ANSYS Tip of the Week
What is a PSD Spectrum
bullA PSD spectrum is a statistical measure of the responseof a structure to random dynamic loading conditions Itis a graph of the PSD value versus frequency where thePSD may be a displacement PSD velocity PSDacceleration PSD or force PSD Mathematically the areaunder a PSD-versus-frequency curve is equal to thevariance (square of the standard deviation of theresponse)
Introduction
CSI ANSYS Tip of the Week
Introduction
Sample PSD Curves
Sample Acceleration PSD Curve
0
001
002
003
004
005
006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
Sample Acceleration PSD Curve
0
0001
0002
0003
0004
0005
0006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
bull Outlinendash Introductionndash Sample Problem
bull Descriptionbull Pre Processing Steps Omittedbull Interactive steps
ndash Specify Modal Analysis
ndash Specify Modal AnalysisOptions
ndash Constrain Board
ndash Solve Modal
ndash Specify Spectrum Analysis
ndash Specify Analysis Options
ndash Specify PSD Settings
ndash Specify PSD vs Frequency
Random Vibrationsbull (Continued)
ndash Plot Input PSD
ndash Specify Damping
ndash Flag Nodes to get PSD Input
ndash Solve for Participation Factors
ndash Set PSD Calculation Controls
ndash Solve Random Vibration Solution
ndash Set Mode Combination
ndash Calculate mode combinations and 1sigma response
ndash Post Processing Results Summary
ndash 1 sigma Results
ndash Post Processing 1 sigmaDisplacements
ndash Post Processing 1 sigma Stresses
ndash Plotting Response PSD in Post 26
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis
bullA Random Vibration Analysis is a form of SpectrumAnalysis
bullThe spectrum is a graph of spectral value versusfrequency that captures the intensity and frequencycontent of time-history loadsbullRandom vibration analysis is probabilistic in naturebecause both input and output quantities representonly the probability that they take on certain values
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis(continued)
bullRandom Vibration Analysis uses Power spectral densityto quantify the loading
bull (PSD) is a statistical measure defined as the limitingmean-square value of a random variable It is used inrandom vibration analyses in which the instantaneousmagnitudes of the response can be specified only byprobability distribution functions that show theprobability of the magnitude taking a particular value
CSI ANSYS Tip of the Week
What is a PSD Spectrum
bullA PSD spectrum is a statistical measure of the responseof a structure to random dynamic loading conditions Itis a graph of the PSD value versus frequency where thePSD may be a displacement PSD velocity PSDacceleration PSD or force PSD Mathematically the areaunder a PSD-versus-frequency curve is equal to thevariance (square of the standard deviation of theresponse)
Introduction
CSI ANSYS Tip of the Week
Introduction
Sample PSD Curves
Sample Acceleration PSD Curve
0
001
002
003
004
005
006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
Sample Acceleration PSD Curve
0
0001
0002
0003
0004
0005
0006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis
bullA Random Vibration Analysis is a form of SpectrumAnalysis
bullThe spectrum is a graph of spectral value versusfrequency that captures the intensity and frequencycontent of time-history loadsbullRandom vibration analysis is probabilistic in naturebecause both input and output quantities representonly the probability that they take on certain values
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis(continued)
bullRandom Vibration Analysis uses Power spectral densityto quantify the loading
bull (PSD) is a statistical measure defined as the limitingmean-square value of a random variable It is used inrandom vibration analyses in which the instantaneousmagnitudes of the response can be specified only byprobability distribution functions that show theprobability of the magnitude taking a particular value
CSI ANSYS Tip of the Week
What is a PSD Spectrum
bullA PSD spectrum is a statistical measure of the responseof a structure to random dynamic loading conditions Itis a graph of the PSD value versus frequency where thePSD may be a displacement PSD velocity PSDacceleration PSD or force PSD Mathematically the areaunder a PSD-versus-frequency curve is equal to thevariance (square of the standard deviation of theresponse)
Introduction
CSI ANSYS Tip of the Week
Introduction
Sample PSD Curves
Sample Acceleration PSD Curve
0
001
002
003
004
005
006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
Sample Acceleration PSD Curve
0
0001
0002
0003
0004
0005
0006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Introduction
What is a Random Vibration Analysis(continued)
bullRandom Vibration Analysis uses Power spectral densityto quantify the loading
bull (PSD) is a statistical measure defined as the limitingmean-square value of a random variable It is used inrandom vibration analyses in which the instantaneousmagnitudes of the response can be specified only byprobability distribution functions that show theprobability of the magnitude taking a particular value
CSI ANSYS Tip of the Week
What is a PSD Spectrum
bullA PSD spectrum is a statistical measure of the responseof a structure to random dynamic loading conditions Itis a graph of the PSD value versus frequency where thePSD may be a displacement PSD velocity PSDacceleration PSD or force PSD Mathematically the areaunder a PSD-versus-frequency curve is equal to thevariance (square of the standard deviation of theresponse)
Introduction
CSI ANSYS Tip of the Week
Introduction
Sample PSD Curves
Sample Acceleration PSD Curve
0
001
002
003
004
005
006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
Sample Acceleration PSD Curve
0
0001
0002
0003
0004
0005
0006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
What is a PSD Spectrum
bullA PSD spectrum is a statistical measure of the responseof a structure to random dynamic loading conditions Itis a graph of the PSD value versus frequency where thePSD may be a displacement PSD velocity PSDacceleration PSD or force PSD Mathematically the areaunder a PSD-versus-frequency curve is equal to thevariance (square of the standard deviation of theresponse)
Introduction
CSI ANSYS Tip of the Week
Introduction
Sample PSD Curves
Sample Acceleration PSD Curve
0
001
002
003
004
005
006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
Sample Acceleration PSD Curve
0
0001
0002
0003
0004
0005
0006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Introduction
Sample PSD Curves
Sample Acceleration PSD Curve
0
001
002
003
004
005
006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
Sample Acceleration PSD Curve
0
0001
0002
0003
0004
0005
0006
1 10 100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Introduction
How does one obtain a PSD Spectrum
bullPSD spectrum curves are generally supplied as a specor are measured and calculated using vibration analysisequipment
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Sample Problem
The following steps will detail running through asimple PSD analysis using the GUI An input filewith every command is included at the end of thisdocument
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board exposed to a Base Acceleration Power SpectralDensity (g^2Hz) input in the global Z direction (normal toboard) on 4 corners as show below
Input Acceleration PSD
100
400 1200
2500
0
001
002
003
004
005
006
100 1000 10000
Frequency (Hz)
PSD
(g^2
Hz)
PSD
PSD
PSD
PSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Sample Problem Description
bullCircuit Board with 3 components
bullBoard Constrained at 4 corners in all DOF
bullDamping Ratio = 2
bullModel meshed with Solid92 10 noded tetrahedrons
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
bullPreprocessing steps - Details omitted
bullImport Geometry Glue Volumes Define MaterialProperties Assign Material Attributes Set Element TypeMesh Model
bullSolution steps - Step by Step starting on next slide
Sample Problem Description
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify Modal Analysis
bullPick Modal
ANSYS Main Menugt Solution gt New Analysis
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify Modal Analysis Options
bullPick Modal Extraction Method(Block Lanczos a good choice)
bullSpecify 20 modes to extract
bullExpand all modes
bullCalculate Element results
ANSYS Main Menugt Solution gt Analysis Options
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Constrain Board
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
bullConstrain All DOF (UXUYUZ)
ANSYS Main Menugt Solution gt Apply gt Displacement gt On Nodes
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Solve ModalANSYS Main Menugt Solution gt Solve
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify Spectrum AnalysisANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt New Analysis
bullPick Spectrum
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify Analysis OptionsANSYS Main Menugt Solution gt Analysis Options
bullSpecify PSD
bullSpecify the number ofmodes from the modalto include in the PSDanalysis
bullSpecify to CalculateElement Results(stresses strainsetc)
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify PSD SettingsANSYS Main Menugt Solution gt Spectrum gt PSD gt Settings
bullInput data will be interms of g^2Hztherefore specify thissetting
bullAnalysis has one PSDtable therefore leavetable number to 1
bullSpecify Value ofacceleration due togravity (g)
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify PSD vs FrequencyANSYS Main Menugt Solution gt Spectrum gt PSD gt PSD vs Freq
bullSpecify 1 for the PSDTable (only one table inthis analysis)
bullEnter Frequency andValue data
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plot Input PSDANSYS Main Menugt Solution gt Spectrum gt PSD gt Plot
bullSet table to 1
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Specify DampingANSYS Main Menugt Solution gt TimeFrequency gt Damping
bullSpecify 2 ConstantDamping Ratio
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullPick the 4 corner nodes on thebottom side of the board
bull1748
bull1782
bull1902
bull2038
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Flag Nodes to get PSD Input
bullSpecify Excitation direction to ZNote This will flag a 1 displacement onthe node telling ANSYS the previouslydefined PSD table is to be applied Youcan apply base excitations only at nodesthat were constrained in the modalanalysis
bullUXUY =0 Constraints on these4 nodes are left over from ModalAnalysis and remain throughPSD Analysis No need to re-specify them
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Base PSD Excit gt On Nodes
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Solve for Participation Factors
bullSpecify 1 for table
bullSpecify Base excitation Problem
bullLeave parcor to default Notrequired for single PSD excitation
Note This step Calculates theparticipation factors for thespecified PSD table
ANSYS Main Menugt Solution gt Apply gt Spectrum gt Calculate PF
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Set PSD Calculation Controls
bullSpecify all Solution items areto be calculated Relative toBase This means the inputexcitation is subtracted outInput nodes have their resultsreported as zero
Note
These specifications are for thegeneral postprocessor resultsnot the time historypostprocessor
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Calc Controls
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
ANSYS Main Menugt Solution gt Solve gt Current LS
Solve Random Vibration Solution
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Set Mode Combination
bullLeave significance at 0
bullAll 20 modes will be used inmode combination
ANSYS Main Menugt Finish
ANSYS Main Menugt Solution gt Spectrum gt PSD gt Mode Combine
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Calculate mode combinations and 1 sigma response
ANSYS Main Menugt Solution gt Solve gt Current LS
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Post Processing Results SummaryANSYS Main Menugt General Post Processor gt Results Summary
bullLoad step 1 - modal results
bullLoad step 2 - unit static solutions
bullLoad step 3 - 1 sigma displacementsstrains stresses
bullLoad step 4 - 1 sigma velocities
bullLoad step 5 - 1 sigma accelerations
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
1 sigma Results
1σ results are typically used forbull First passage failure calculations
ndash What is the probability that the displacement at a DOF will exceeda displacement limit in a given time period
bull Fatigue calculationsndash Based on the premise that the stress level is at or below 1σ 682
of the time between 1σ=and 2σ 272 of the time (954-682)and between 2σ=and 3σ 43 of the time (997-954) and above3σ=less than 3 of the time
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Post Processing 1 sigma Displacements
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtDOF Solution gt USUM
bull1 sigma board deflection = 002rdquo
bull3 sigma board deflection = 3 002rdquo= 006rdquo
bullTherefore only 3 of the timeboard deflection will exceed 006rdquo
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Post Processing 1 sigma Stresses
ANSYS Main Menugt General Post Processor gt Plot Results gt Nodal SolutiongtStress gt SEQV
bull1 sigma corner stress = 698 psi
bull3 sigma corner stress = 3 698 psi=2094 psi
bullTherefore only 3 of the time boardcorner stress will exceed 2094 psi
bullNote For simplicity in this model thecorner nodes are constrained Thiscreates singular stress results Inreality modeling and holding the actualmounting hold would provide moreaccurate results
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Store Data
bullThis command sets the resolution ofthe frequency vector for the PSD curve10 gives finer results 1 gives coarserresults 5 is the default
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
bullThis command defines the variablesthat we want to see as a function oftime or frequency
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick one corner node that wasconstrained 1748 is picked in thiscase
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called base
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Pick node 350 on top of component
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Define Variables
Specify UZ DOF and specify a label in this case label is called Node_350
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 2 is the corner node baseexcitation
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Calculate Resp PSD
bullSpecify new variable number tostore PSD in
bullSpecify existing variable numberthat has DOF solution In thiscase 3 is the node on top of acomponent
bullSpecify the response to beacceleration
bullSpecify absolute in order to plotinput PSD and response PSDtogether
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 7 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 4 to operateon This has the input PSD inin^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Math Operations
bullConvert results fromin^2sec^4Hz into g^2Hz bydividing results by 1g^2 =138642
bullSpecify variable 8 gets theresults of this operation
bullSpecify 1g^2 factor
bullSpecify variable 5 to operateon This has the componentnode PSD in in^2sec^4Hz
bullGive new variable a label
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
Plot Controls gt Style gt Graphs gt Modify Axes
bullDefine labels for graph
bullSet axes to Logarithmic
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot input PSD (g^2Hz)variable 7
bullPlot response PSD (g^2Hz)variable 8
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
CSI ANSYS Tip of the Week
Plotting Response PSD in Post 26
ANSYS Main Menugt Time History Post Processor gt Graph Variables
bullPlot shows the response PSD ofthe component on the boardversus the input PSD at one ofthe corner nodes
bullFrom this plot we see thedynamic amplification the circuitboard provides from the inputPSD
