University of WashingtonMechanics of Materials LaboratoryPPME 354 x xyxzxy y yzxzyzzCourse website: http://swhite.me.washington.edu/~jenkinsm/me354/Department of Mechanical EngineeringUniversityof WashingtonSeattle, WashingtonMichael G. JenkinsAssociate Professor, Mechanical EngineeringTEL: 206-685-7061; FAX: 206-685-8047; e-mail: jenkinsm@u.washington.eduRev2.001 January 2001Mechanical Engineering 354Mechanics of Materials LaboratoryTABLEOFCONTENTSTopic Page1. Introduction....................................................................................................1.1Laboratory ProcedureLaboratory Report2. Stress/Strain/Constitutive Relations...........................................................2.1StressStrainConstitutive Relations3. Beams: Stress, Strain, Deflection (Lab Exercise) ....................................3.1StrainStress: Normal and ShearDeflections4. Beams: Curved, Composite, Unsymmetrical Bending (Lab Exercise) 4.1Curved BeamsUnsymmetrical BendingCompositeBeams5. Mechanical Properties and Performance of Materials(Tension, torsion, hardness, impact tests) (Lab Exercise).......................5.1Mechanical TestingTensionHardnessTorsionImpactPlasticity Relations6. Stress Concentration and Stress Raisers (Lab Exercise) .......................6.1Stress Concentration FactorsEffects of Stress RaisersExperimental Techniques7. Fracture and Effects of Cracks (Lab Exercise)...........................................7.18. Time Dependent Behaviour: Creep Deformation(Lab Exercise)........8.19. Time Dependent Behaviour: Cyclic Fatigue(Lab Exercise)..................9.1Topic Page10. Compression and Buckling of Columns (Lab Exercise)........................10.111. Structures: Complex Stresses and Deflections (Lab Exercise)...........11.1Failure CriteriaCombined StressesTypes of Engineering Structures12. Pressure Vessels: Combined Loading (Lab Exercise) ........................12.1Thin-Walled Pressure VesselsThick-Walled Pressure Vessels13. References................................................................................................... R.1Appendix A: Lab Report Format ............................................................. A.1Appendix B: Lab Exercise Handouts...................................................... B.11.1MECHANICSOFMATERIALSLABORATORYNOTES1.INTRODUCTIONMechanics of Materials is generallythenameappliedtoadiscipline inwhichthestress,strain and deflections of loadedstructuralelementsareconsidered. Thissetofnotes presentsthe laboratory aspects of this subject.Fornearlyalldesignworkitisnecessarytoknowsomethingoftheelasticand,often,plastic properties ofthematerialtobeused. Whilethesepropertiesareoftenavailablefromhandbooks, sometimesparticularpropertiesoflesscommonmaterialsareneeded,inwhichcasetheengineermustperformhisowntests. Theperformance ofthesetypicaltestsinthislaboratory will give a better feeling for the significanceofthevarious materialpropertiesandforthe accuracy with which these quantities can be determined.Thevarioussectionsofthesenotesareconcernedwithreviewofthesubjectofmechanicsofmaterialsandrelatedmaterialpropertiesincludingthelaboratoryapplicationoftheseprinciplestoasimplestructures.Invariousexercises,thestresses,strainsanddeflectionsofabothsimply-supportedstraightandcurvedbeamsaremeasuredandcomparedtoanalyticalpredictions.Inanotherexercise,selectedmechanicalpropertiesandperformanceofrepresentativeengineeringmaterialsaremeasuredusingstandardizedtestmethodsandquantitativelycomparedtohandbookvalues.Theeffectsofstressconcentrationsarethefocusofanother exerciseinwhichphotoelasticityisusedtodeterminestress raisers for comparisons to values obtained fromcompendiums. Fracture mechanics andcrack interactions are examined in a study of the load carrying reduction of cracks incomponents.Time-dependentbehaviourisevaluatedthroughmeasurementandanalysisofcreepdeformationandcyclicfatiguefailures.Structuralinstabilitiessuchascolumnbucklingarecomparedtomaterialstrengthinassessingengineeringfailures.Complexstructuresareanalyzedthroughexperimentalmeasurementsandbothsimpleandcomplexanalyticalmethods to assess the implications of oversimplifications in engineering analysis.Laboratory ProcedureMechanicsofMaterialsLaboratory,ME354,isintendedtogiveanexperimentalunderstanding and verification of thecourseworkcovered inMechanicsofMaterials,CIVE220(formerly ENGR 220) and Introduction toMaterialsScience,MSE170(formerlyENGR170).No one should be enrolled in this coursewho hasnottakenorisnotcurrentlytakingMSE170and CIVE 220 or their equivalents.1.2Because of the nature of the laboratory experiments,it is necessary toconductthemasa class activity with students either observing ordirectlyparticipatingintheexercises. In someexercises, small by groups of students will conduct the experiment directly. Inotherexercises,theinstructorwilltake theleadinoperatingtheequipmentwithsomestudentsparticipatingasassistants and others as observers andrecorders. An instructorwill alwaysbeavailableinthelaboratorytointroducetheexercise,describetheoperationoftheequipment,discusstheexpectedresultsandpresent thesalientaspects oftheanalysis. Generally,studentswillbeexpected to work as teams when required but must complete written reports independently.Somelaboratoryexercisesrequireformalwrittenreports. Otherexercisesrequirethecompletionofpre-formattedlabreportsandtheirtransmittaltotheinstructorintheformofashort memo report Still other exercises require only the completion ofpre-formattedwrite-upswithout any additional writing.All lab reports, regardless of type, must be turned intoreceive apassing course grade.Missinglabreports atthe timeofassignmentoffinal gradeswillmeantheassignmentofafinalgradeofXforonequarterfollowingthecourse,regardlessofthequalityoftherestofthecoursework,untilallreportsarein.Failuretocompletemissinglabreports or to make other arrangements after one quarter has passed following completion of thecourse will result in the conversion of the X to a 0.0.Laboratory reportsReports are the primary basis for the course grade.Examinationgradesanddiscussionparticipationarealsoconsideredinthefinalgrade. Gradesareimportanttothestudentforarelatively short time; report writing will be important to the student's total career.Thelaboratoryreports provideanopportunityforthestudenttosharpenwritingskillsandtoincrease theawarenessofwritingstandards.Futureemployerswillrequirestandardsandwilljudgeyourprofessionalortechnicalabilityinpartonyourreportingcapabilities.Sherman (Sherman et al, 1975) has stated "It would be an overstatement, perhaps, to saythatacareerinatechnicalprofessionwillbeimpossibleifyoucannotwriteeffectively.Itisnooverstatement,however, tosay that weaknessinwritingisahandicapthatwillweakenyourqualifications for many desirable positions, and that skill in writingisanassetthat canmakeyourprofessional advancement faster and easier."Technicalwritinginvolvesstyle,neatness,grammar,usageofwords,spelling,andformat.Of these attributes, first five aregenerallyapplicable,whereasthesixth(i.e.,format)isspecific to the particularapplication. Inthecourse,theformatisnonarbitraryandisdetailedinthe appendix.Neatness:All written communications should be neat intheirfinal form. Reportsshouldbe machine generated.Original data maybeinpencilandisalwaysincluded intheappendixof the report.1.3Grammar:Sentencestructure,paragraphconstruction,andpunctuationpresumablyhave been learnedpriortotakingME354. Errorsingrammarwillbenotedbythegradersothat the student's writing skills will be improved.Usage of Words:Misuse ofwordsinvolveswordsandphrasesthatare problemsformanywriters. Afew examplesofsuch"pairs"are:affect-effect,among-between,because-for, fewer-less, like-as if, percent-portion, while-although, too-two, their-there.Jargon is acceptable when properly used (i.e., not overused!).Specializedwordsareacceptabletoaparticularprofessionbutshouldnotbeusedtoimpressan"outsider."Debasing of the Englishlanguagebytheuseofsuffixessuchas"ise"and"wise"isconfusingand unnecessary.Colloquialisms or contractions should not be used in formal technical writing.Style:Thestyleofwritingisdeterminedbythepotentialreader.Areportmaybeformalorinformal,childishormature,personalorimpersonal,stiltedoradmirable,wordyorsuccinct.The formal laboratory report may be read by a teaching assistant or a professor,but itshouldbewrittenforanengineeringmanager.Properlywrittenlaboratoryreportsmaybeused for reference material; well-written reports will enhance this value.Do not copy portions of these notes word forwordinyourreport. Statementsin"yourownwords"willindicateunderstandinganddescriptiveconcisenessability.Theuseoffuturetenseortelling"whatyouaregoingtodo"doesnotbelonginareportofwhatyoudid.Generally the tenseofreports is suchthatanythinginthereport(e.g.,tables, figures,section)are referredtointhepresent tense. Anything done toproducethe resultsofthereports isinthe past tense.Traditionally,technicalreportwritinghasbeenconductedinthethirdpersonpassivevoice (e.g., "The tests were conducted"). Theuseof"I" impartsapersonaltonetothereportwhichisgenerallyinappropriate.Firstpersonstyleemphasizesthewriter'spartintheexperimentortestratherthanthematerialorequipmentused."I"and"we"aresometimesused to reduce awkward or stilted language (such as using "one").Such useshouldbekept toa minimum, particularly in the Summary.Spelling:Spelling words properly isaproblemformanystudents. Incorrectlyspelledwords,particularlysimplewords,indicateajuvenileapproachtotechnicalwriting.ToquoteSherman (Shermanetal,1975),"Evenaweakspeller,ifhekeepsalistofthewordsthathemisses, isusuallysurprised atitsshortness....Hecanofteneliminatemostofhiserrorsb ylearning to spell no morethan40or50words."Keepinmindthatelectronicspell checkersdonot have any bearing on word choice.The wrong word correctly spelled is still the wrong word.Wordsfrequentlymisspelledinthiscourseinclude:yield,specimen,temperature,Riehle, recommend, omission to name just a few.The use of a word guide is strongly urgedfor those students with a spelling problem.