High-Temperature Strain Sensing for Aerospace Applications · PDF file ·...
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HighHigh--Temperature Strain Sensing Temperature Strain Sensing for Aerospace Applicationsfor Aerospace Applications
Anthony (Nino) Piazza, Dr. Lance W. Richards, Larry D. HudsonNASA Dryden Flight Research CenterSummer WRSGC in Bethlehem, PA
August 18-20, 2008
https://ntrs.nasa.gov/search.jsp?R=20080037427 2018-05-13T20:39:18+00:00Z
Dryden Flight Research Center
•
Background•
Objective
•
Sensors•
Attachment Techniques
•
Laboratory Evaluation / Characterization
•
Large-Scale Structures
Outline
Dryden Flight Research Center
LowMediumHigh
LowMediumHigh
FoilStrain Gage
WeldableStrain Gage
Wire WoundStrain Gage
Silica Fiber Optic Strain Gage
2000
Sapphire Fiber Optic Strain Gage
30001000
Difficulty of InstallationHot Structures
Strain MeasurementArea of Need
Com
mer
cial
ly A
vaila
ble
Strain Sensor Type
Difficulty of Use
LowMediumHigh
LowMediumHigh
FoilStrain Gage
WeldableStrain Gage
Wire WoundStrain Gage
Silica Fiber Optic Strain Gage
2000
Sapphire Fiber Optic Strain Gage
30001000
Difficulty of InstallationHot Structures
Strain MeasurementArea of Need
Com
mer
cial
ly A
vaila
ble
Strain Sensor Type
Difficulty of Use
Lack of Capability•
TPS and hot structures are utilizing advanced materials that operate at temperatures that exceed our ability to measure structural performance
•
Robust strain sensors that operate accurately and reliably beyond 1800°F are needed but do not exist
Implication•
Hinders ability to validate analysis and modeling techniques•
Hinders ability to optimization structural designs
Background Sensor Development Motivation
Dryden Flight Research Center
Provide strain data for validating finite element models and thermal-structural analyses
•
Develop sensor attachment techniques for relevant structural materials at the small test specimen level
–
Apply methods to large scale hot-structures test articles•
Perform laboratory tests to characterize sensor and generate corrections to apply to indicated strains
Objective Measurements Lab
Dryden Flight Research Center
High-Temp Quarter-Bridge Strain Gage
Pro’s•
Sturdy / rugged thermal sprayed installation and spot-welded leadwire stakedown
•
Available high sample rate DAS, usually AC coupled to negate large ξapp
Con’s•
Large magnitude ξapp
primarily due to wire TCR, slope rotates cycle-to-cycle
•
Sensitivity (GF): Function of temperature
Apparent Strain = [TCRgage / GFset + (αsub - αgage)] * (ΔT)
R1
R3 R2
R4
+ EX
- S + S
- EX
Red
Black
WhiteGreen
Wheatstone Bridge
(Δ R / R) * GF = RTξ
Sensors Dynamic Measurements (Max Op 1850°F)
-15000
-12000
-9000
-6000
-3000
0
0 500 1000 1500Temp (F)
Str
ain
()
1st Cycle2nd Cycle3rd Cycle
-14000
-13000
-12000
-11000
-10000
800 1000 1200 1400 1600
1st Cycle2nd Cycle3rd Cycle
PTZ
RotationDirection
Heat / Cool Rate:1 °F / sec
-15000
-12000
-9000
-6000
-3000
0
0 500 1000 1500Temp (F)
Str
ain
()
1st Cycle2nd Cycle3rd Cycle
-14000
-13000
-12000
-11000
-10000
800 1000 1200 1400 1600
1st Cycle2nd Cycle3rd Cycle
PTZ
RotationDirection
Heat / Cool Rate:1 °F / sec
Dryden Flight Research Center
Strain / LG (initial), where sensitivity = LG
Apparent Strain (ξapp) = (αsub - αfiber) * ΔT
LC
CeramicAttach
LG
Extrinsic Fabry-Perot Interferometer (EFPI)Commercially Available
Sensors Static Measurement (Max Op 1850°F)
SM gold coated fiber 125μm dia, 6μm core 840nm tuned
Silica micro-capillary:OD = 285μm ID = 130μm
840nm, 50μW
Strain = δLC
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BB OpticalSource
PowerSplitter
DiffractionGratingMini
Spectrometer
Lens
CCDOut to Signal
Processor
Single Mode EFPI Signal Conditioning
Sensors Static Measurement
Dryden Flight Research Center
Sensors Static Measurement (Max Op 600°F)
Reflected λ
Reflected λTensile Load
ε
λ
ε
λ
BBR
E
Freq / Dist
DiodeTunable
Laser
FFTE
λ
IFFTStrain (με)(δλ / λ) x 0.725
Unstrained
SM Polyimide Coated Fiber125μm dia, 9μm core, 1550nm
2 x 1Coupler
Dryden Flight Research Center
Develop sensor attachment techniques for relevant structural materials
•
Derive surface prep and optimal plasma spray parameters for applicable substrate
–
i.e., powder media / type, power level, traverse rate, feed rate, and spraying distance
•
Or, optimize / select cement that best fits application•
Improve methods of handling and protecting fragile sensor during harsh installation processes
Attachment Techniques Applications Above 600°F
Dryden Flight Research Center
Attachment Techniques Thermal Spray vs. Cement
Thermal sprayed attachments are preferred even though cements are simpler to apply
•
Cements are often corrosive to TC or strain gage alloys–
Si / Pt, NaF
/ Fe-Cr-Al alloys, alkali silicate / Cr
•
Tests indicate increased EFPI gage-to-gage scatter on first cycle
Positive lead ofK-Type TC (NiCr)
Post-Test: One cycle to 2550°F
•
Cements are more prone to bond failure due to shrinkage and cracking caused when binders dissipate
Dryden Flight Research Center
Thermal Spray Room•
80KW Plasma System•
Rokide Flame-Spray System•
Powder Spray System•
Grit-Blast Cabinet•
Micro-Blast System•
Water Curtain Spray Booth
Attachment Techniques Thermal Spray Equipment
Dryden Flight Research Center
Arc-plasma sprayed base coat•
Metallic Substrates: Used to transition high expansion substrate
metal with low expansion sensor attachment material (Al2
O3
)•
CMC Substrates (inert testing): High melting-point ductile transitional metals (i.e. Ta, TiO2
, & Mo) more conducive for attachment to smooth surfaces like SiC
Rokide flame-sprayed sensor attachment•
Applies a less dense form of alumina
than plasma spraying•
Electrically insulates (encapsulate) wire resistive strain gages
Collaborative work has been done through grants with Dr. Richard Knight, Drexel University
Attachment Techniques Thermal Spray
Dryden Flight Research Center
Attachment Techniques Wire Strain Gage Installation
Place SG on thermal sprayed basecoats via carrier tape
Apply flame-sprayed tack and cover coats
Spot weld three- conductor leadwire
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8.5mm
0.35”
Attachment Techniques Fiber Optic EFPI Installation
Flame-spray sensor attachment
Transfer to thermal sprayed base coat using carrier tape
Fabricate sensor under microscope
Dryden Flight Research Center
Attachment Techniques Fiber Optic EFPI Installation
1. Plasma Spray Basecoat (2-mil)
2. Rokide Flame- Spray Intermediate Layer (1-mil)
3. Set EFPI Sensor in Place Using Carrier Tape
4. Rokide Flame-Spray Attachment Layer (minimal coverage)
Dryden Flight Research Center
Refrasil Overbraid
Two applications of MB610 sufficiently coat fiber (Cured @ 270°F)
Bonded FBG’s Type-K TC
Polyimide coated EFPI bonded with mixture of
GA-61 and MB610
Attachment Techniques Applications Below 600°F
4-in
Dryden Flight Research Center
Validate and characterize strain measurement•
Base-line / characterize high-temperature strain sensors on monolithic Inconel specimens
–
Known material spec’s isolate substrate from inherent sensor traits prior to testing on more complex composites
•
Evaluate / characterize sensitivity (GF) of strain sensors on ceramic composite substrates using laboratory combined thermal / mechanical load fixture
•
Generate apparent strain curves for corrections of indicated strains on relevant ceramic composite hot-structures
Evaluation / Characterization
Dryden Flight Research Center
Clamping Beam
Loading MandrelsSide ALoading
Side BLoading
13 in.
Clamping Beam
Loading MandrelsSide ALoading
Side BLoading
13 in.
Clamping Beam
Loading MandrelsSide ALoading
Side BLoading
13 in.
Evaluation / Characterization Combined Thermal / Mechanical Loading (Obsolete)
Thermal / Mechanical Cantilever Beam Testing of EFPI’s•
Excellent correlation with SG to 550°F (3%)•
Very little change to 1200°F•
Slight drop in output slope above 1200°F•
Maximum gap readability uncertain at upper range temperatures on high expansion material
-1200
-600
0
600
1200
-0.200 -0.100 0.000 0.100 0.200
Deflection (in.)
Stra
in (u
e)
Ave SG
L02
L02 (KSo)
Tension
Compression
Standoff Correction FactorKSo = c/(c+So) = 0.189 / 0.189 + 0.0055 = 0.972 where: c = Distance from Neutral axis So = Distance from centerline of fiber (in tube) to substrate
FS2000 SettingsExtended Range: ONGap Limit: OFFSample Interval: 100msAnalog Out: On (1:0.1)
EFPI Combined Loading on IN625
Loading Mandrels
LVDT’sExtensions
ClampingBeam
LoadBar
TOP VIEW
1800°F, Air Only
Dryden Flight Research Center
Furnace / cantilever beam loading system for sensitivity testing
•
Air or inert (3000°F max)•
12-in3
inner furnace with Molydisilicide
elements
•
Micrometer / mandrel side loading•
LVDT displacement measurements•
POCO Graphite hardware for inert environment testing of ceramic composites
•
IN625 hardware for metallic testing in air•
Sapphire viewing windows
LoadingMandrel
LVDT
Clamping Beam
Constant Strain Load Bar
Evaluation / Characterization Combined Thermal / Mechanical Loading (Current)
Dryden Flight Research Center
Sensor Characterization Air or inert (3000°F max)
•
Evaluate bond integrity•
Generate ξapp correction curves•
Evaluate sensitivity and accuracy•
Evaluate sensor-to-sensor scatter, repeatability, hysteresis, and drift
Modified Dilatometer System
4 EFPI’s on C-C
Evaluation / Characterization Dilatometer Testing
Dryden Flight Research Center
ξapp Correction: Removal of inherent sensor traits and substrate expansion from indicated strain to acquire true strains or thermal stresses
ξtrue = ξindicated – ξapp, where ξapp = (αsub - αfiber) * ΔT•
Inconel (LH chart): Large expansion differential between IN601 and Si –
output primarily substrate expansion, CTE * ΔT
•
CMC (RH chart): Small expansion ratio between C-SiC and Si–
requires correction for fiber expansion (lessening cavity gap)
•
Graphs demonstrate how well actual ξapp curves followed theoretical
0
4000
8000
12000
16000
0 400 800 1200 1600
Temp (F)
Stra
in (u
e)
-500
-250
0
250
500
Dev
iatio
n fr
om C
oupo
n Ex
pans
ion
Coupon (dL/L)EFPI 3EFPI 4Dev EFPI 3Dev EFPI 4
Heating rate: 7.2 °F/minCoupon Substrate: IN601
File: LC2a900C1
Inconel Substrate
y = 1E-10x4 - 2E-07x3 + 0.0006x2 + 0.3096x - 30.1290
500
1000
1500
2000
2500
0 600 1200 1800
Temp (F)
Stra
in ( μ
ε)
Coupon DL/L
Average all FO
Theoretical Eapp
CMC Substrate
Evaluation / Characterization EFPI Apparent Strain
Dryden Flight Research Center
Evaluation / Characterization FBG Apparent Strain
y = 0.0044x2 + 3.6664x - 302.93
0
500
1000
1500
2000
2500
0 100 200 300 400 500
Temp (F)
Stra
in ( μ
ε)
Theoretical Thermal Out
Average Eapp (12)
Poly. (Average Eapp (12))Thermal Out (unbonded) = (α fiber + ξ / Pe) * ΔT
where:Thermal Optic Effect (ξ) = 3.78 με/FStrain Optic Constant (Pe) = 0.725
FBG on Graphite/Epoxy Composite0
500
1000
1500
2000
2500
9:21:36 9:28:48 9:36:00 9:43:12 9:50:24 9:57:36 10:04:48
Time
Stra
in ( μ
ε)
Bonded to substrate
Not bonded to substrate
Heating/Cooling Rate: 0.5F/sec
Dryden Flight Research Center
Large Scale Structures Ceramic Composite Control Surfaces
C/C Control SurfaceMarch, 2003C/C Control SurfaceMarch, 2003
C/SiC BodyflapNov, 2003
C/SiC BodyflapNov, 2003
X-37 C/C FlaperonSubcomponent
August, 2004
X-37 C/C FlaperonSubcomponent
August, 2004
X-37 C/SiC FlaperonSubcomponentMay, 2004
X-37 C/SiC FlaperonSubcomponentMay, 2004
2000°F2000°F
2400°F2400°F 2300°F2300°F
2100°F2100°F
X-37 C/C Flaperon Qual UnitAugust, 2005
X-37 C/C Flaperon Qual UnitAugust, 2005
2500°F2500°FC/C Control SurfaceMarch, 2003C/C Control SurfaceMarch, 2003
C/SiC BodyflapNov, 2003
C/SiC BodyflapNov, 2003
X-37 C/C FlaperonSubcomponent
August, 2004
X-37 C/C FlaperonSubcomponent
August, 2004
X-37 C/SiC FlaperonSubcomponentMay, 2004
X-37 C/SiC FlaperonSubcomponentMay, 2004
2000°F2000°F
2400°F2400°F 2300°F2300°F
2100°F2100°F
X-37 C/C Flaperon Qual UnitAugust, 2005
X-37 C/C Flaperon Qual UnitAugust, 2005
2500°F2500°F
Dryden Flight Research Center
Large Scale Structures Metallic Dynamic Environment
C-17 Engine Testing•
Test temperatures above 1100°F•
Engine intentionally unbalanced creating large peak-to-peak vibrations
X-33 Sonic Fatigue Testing•
Dynamic loads as high as -158db•
Test temperatures above 1500°F•
High transient heating rates producing large thermal stresses
Dryden Flight Research Center
Large Scale Structures Fiber Optic Wing Shape Sensing
NASA Dryden Predator B (Ikhana)
ξapp coupon tested from -60°F to 150°F