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1、Lab4:Stressvs.StrainLabLucienFilipThepurposeofthislabwastodrawdifferentconclusionsaboutthepropertiesofasteelbar.Duringthelabweuseda¾inchby18inchbarof1020HRsteelandtesteditusingaUniversalTestingMachine.ThismachinewaslocatedintheStrengthandMaterialsLaboratory.Usingtheresultsrecorded,wehadt
2、ocreateastressvs.straingraphandcalculatethemodulusofelasticity.Toconductthislab,weattachedthe1020HRsteelbartoauniversaltestingmachine.Then,theinstructedfastenedanextensometertothebar.Theextensometerisusedtomeasuretheslightestchangeoflengththatanobjectundergoes.Oncethesteelbarwascorrectly
3、hookeduptotheuniversaltestingmachine,webegantoapplyaloadtopullthesteelbar.Weappliedtheloadin1000lbsincrementsuntilitreached21,000lbsandrecordedtheresults.Atthispoint,theinstructorremovedtheextensometerandbegantomeasurethechangeinlengthusingagauge.Withthisgaugewebeganrecordingtheresultsev
4、ery.1inchuntilthesteelbarbroke.Withthedatarecordeduptothepointofbreakage,thenextobjectivewastocreateastressvs.straindiagramandcalculatethemodulusofelasticity.Withtheresults,thenextstepwastoconvertthedataintostressandstrainfigures.Inordertofindthestrainweusedtheequation,.Where,erepresents
5、theelongationandgagelengthistheinitiallengthofthebar,8in.Todeterminethestressweusedtheequation,.Whereas,theforcewastheloadappliedand.UsingtheseLab4:Stressvs.StrainLabtwoformulas,thedatawasthengraphedusingaStressvs.Straindiagram.Thisdiagramshowsusthattheultimatestressisaround70,000psiandt
6、herupturedstressisaround50,000psi.Themodulusoftoughnessisrepresentedbytheareaunderneaththecurveinthediagram.Thelaststepinthislabwastofigureoutthemodulusofelasticityforthe1020HR3/4inchbarofsteel.Inordertodothis,thesamedatausedintheStressvs.StrainDiagramwasgraphedbutonlyuptoaround50,000psi
7、,theyieldpointofthesteel.ThisdiagramisknownastheModulusofElasticity,whichisalsoknownasJoung’sModulus.Theactualmodulusistheslopeofthegraph,where.ThemodulusofElasticitywegotwas30E6.Thisworkedoutperfectlybecausetheactualmodulusofelasticityfor1020HRSis30E6.Usingthisgraphweals
