Stress and StrainWord文档下载推荐.docx
- 文档编号:22149071
- 上传时间:2023-02-02
- 格式:DOCX
- 页数:11
- 大小:67.48KB
Stress and StrainWord文档下载推荐.docx
《Stress and StrainWord文档下载推荐.docx》由会员分享,可在线阅读,更多相关《Stress and StrainWord文档下载推荐.docx(11页珍藏版)》请在冰豆网上搜索。
forrequirementsspecifictoyouroperatingsystem)
∙SCXIBundlefromNationalInstruments(partnumber777448-37)
-LabVIEWFullDevelopmentSystem
-PCI-6024EDataAcquisitionBoard
-SCXI1000chassis
-SCXI1349cable
-SCXI1180feedthroughpanel(notusedinthisexperiment)
∙SCXIModulefromNationalInstruments
-SCXI1121–4ChannelIsolationAmplifier
(partnumber776572-21)
∙SCXITerminalBlockfromNationalInstruments
-SCXI1321–ForusewiththeSCXI1121
(partnumber777687-21)
∙StrainGage
∙Cantileverbeam
∙Metalplate
∙Clamp
∙Masshangerandvarietyofmasses
∙Balanceforaccuratelymeasuringthemasses
∙Websites
-Omega—
-NationalInstruments—
Setup
Computer-basedmeasurementsystemsareusedinawidevarietyofapplications.Inlaboratories,infieldservicesandonmanufacturingplantfloors,thesesystemsactasgeneral-purposemeasurementtoolswell-suitedformeasuringvoltagesignals.However,manyreal-worldsensorsandtransducersrequiresignalconditioningbeforeacomputer-basedmeasurementsystemcaneffectivelyandaccuratelyacquirethesignal.Thefront-endsignalconditioningsystemcanincludefunctionssuchassignalamplification,attenuation,filtering,electricalisolation,simultaneoussampling,andmultiplexing.Inaddition,manytransducersrequireexcitationcurrentsorvoltages,bridgecompletion,linearization,orhighamplificationforproperandaccurateoperation.Therefore,mostcomputer-basedmeasurementsystemsincludesomeformofsignalconditioninginadditiontoplug-indataacquisition(DAQ)devices.Formoreinformationonsignalconditioningforcomputer-baseddataacquisitionsystemsyoucanfindNationalInstrumentsApplicationNote
48onlineat.
TheLabVIEWVIistheStrainVI.Studentsinputthebeamdimensionsandtheappliedload.Thestudentsmustbecarefultouseconsistentunits.ThebridgecircuitisbalancedusingtheoffsetpotentiometerontheVIfrontpanel.UsingtheoffsetpotentiometerispreferabletohavingthestudentsadjusttheoffsetontheSCXI-1321terminalblock.
Figure1.BasicSetupforaBeamUnderaStressLoad
Followthestepslistedtopreparetheworkstationsforthisexperiment.Theinstructionsassumeyouareusingtheequipmentlistshownpreviously.
Note:
MostofthemanualsthatarereferredtoshipwithNationalInstrumentshardwareandsoftware.Ifyoucan’tfindyourhardcopyofthemanuals,youcangetthemonlineatIfyouencounterproblemsduringsetup,contacttechnicalsupportat
BeforetheDayoftheLab
1.Configurethecantileverbeamandweightmeasurementdevice.
a.Thebeamismadeof6061aluminum,butothermaterialscanbeused.Thebeamdimensionsare12.51.00.125inches.
b.Theweightisapplied0.25in.fromthefreeend.
c.Attachthestraingage10.188in.fromthefreeend.
d.Thebeamisclamped11.0in.fromthefreeend.
e.Thebeamisclampedtotheedgeofatable.
f.Ametalplateisusedbetweenthebeamandtheclamp.
2.InstallLabVIEW(seetheLabVIEWReleaseNotesforyourversionofLabVIEW).
3.InstallyourPCI-6024Eboard(seethe6023E/6024E/6025EUserManual).
4.ConfiguretheSCXI1121(seetheSCXI1121UserManual).
a.Enableshuntcalibrationforchannel0.
b.TheSCXI1121hasjumpersettingsthatneedtobemadeforthisexperiment.
i.Setthegaintoanappropriatevalueforyoursensor.Thinkofthegainasascalingfactorthatmakesthesensorvoltagefitwellwithinthemeasurementsystemrange.First,determinethemaximumvoltageoutputofthesensorforthetemperaturerangeitwillexperience.Thendeterminethemaximumvoltagethesystemcanmeasure.Thegainisfoundbydividingthesystemvoltagebythesensorvoltage.Forexample,ifyoursensoroutputsamaximumof0.01voltsandthemeasurementsystemhasarangeof0–10volts,youwouldsetthegainto1000.
ii.Setthejumpersforahalf-bridgecompletionnetworkforchannel0.
iii.Leavetherestofthejumpersintheirfactorysettings.
c.InstalltheSCXI1121intoslot0oftheSCXI1000chassis.
d.Connectthestraingagetochannel0oftheSCXI1321terminalblock.
e.ConnecttheSCXI1321terminalblocktotheSCXI1121module.
5.CablethePCI-6024EtotheSCXI1121modulewiththeSCXI1349(seetheSCXI1349ShieldedInstallationGuide).
6.ConfigurethePCI-6024EboardandtheSCXI1121module(seetheNIDAQReleaseNotesforyourversionofNI-DAQ).
∙WhenconfiguringtheSCXI1121makesurethesoftwaresettingsmatchthejumpersettingsonthephysicalmodule.
7.CreatethefollowingdirectoryinyourLabVIEWfolder:
\\LabVIEW\Experiments\StressandStrain.
8.CopyStressandStrain.llbintotheStressandStrainfolderyoujustcreated.
9.Conductarun-throughofthelabprocedurethestudentswillperform.
OntheDayoftheLab
1.PowerupthecomputerandSCXIchassis.
2.Makesurethestudentshaveenoughmassesattheirworkstations.
References
∙JohnA.Allocca,Transducers:
TheoryandApplications,
RestonPub.Co.
∙Wheeler,AnthonyJ.andGanji,AhmadR.(1996),Introductionto
EngineeringExperimentation,Prentice-HallInc.Englewood
Cliffs,NJ.
Student’sPortion
Introduction
Straingagesareimportanttoanydeviceunderstressorstrain.Straingagesprovidesolutionstomanyrealworldsystemsandtesting.Inthislab,youwillapplyvariousloadstothecantileverbeamandmeasurethestrainusingapre-writtenLabVIEWprogram.
Objective
∙Tousestraingagesformeasurementofstrain.
∙Todeterminethemodulusofelasticityofacantileverbeam.
∙TouseHooke’sLawtodeterminethemodulusofelasticityofanunknownmaterial.
Theory
DesignofStrainGages
Straingagesareusedassensingelementsindisplacementorloadmeasurementsystems.Theycanbeusedtomeasureextremelysmalldeformations.Straingagesaremadeoffinewirewithacertaincross-sectionalarea(A),initiallength(L),andresistivity(ρ).Theresistanceofthewirechangeswhenthewireisdisplacedduetostress.Thestressisanappliedloadactingoverthecross-sectionalareaofthewire.Thefollowingequationdefinestheresistance(R)ofthestraingagewire:
Itiscommontouseagagefactor(G)todescribethechangesinresistance(∆R)ofthestraingageduetochangesinlength(∆L)ofthewire.Thegagefactorisalsousedtocomparevariousstrain-gagematerials:
gagefactor=G=
where
=
isdefinedasstrain
So,strainisthechangeinlengthovertheoriginallength.Theunitsaretypicallymm/mmorin/in.Sometimesthetermμstrain(micro-strain)isused,meaning10-6in/in.
StressandModulusofElasticity(Young’sModulus)
Bymountingstraingagestothesurface(topand/orbottom)ofacantileverbeam,youcanmeasuretheaxialdeformationofthebeam(thedeformationalongthelengthofthebeam)whenatransverseloadisappliedtotheendofthebeam.Theamountofdeformationcanberelatedtothestrainusingthepreviousgagefactorequation.Figure2showsastraingagebondedtothetopsurfaceofthecantileverbeam.
Figure2.CantileverBeamwithaStrainGageMountedontheTop
Whenaload(P)isappliedattheendofthebeam,thetensilestress(σ)alongthex-axisatthetopsurfaceisgivenas:
σ=
(1)
where:
∙M=bendingmoment(unitsofN-m).Mistheproductoftheeffectivebeamlengthandtheforce(P)appliedattheendofthebeam.
∙c=distancefromneutralaxisofbeam(m),Typicallyc=t/2,wheretisthebeamthickness.
∙I=momentofinertiaforacrosssectionofthebeam(unitsarem4).ThemomentofinertiaisI=
.
∙P=load(N).
∙L=effectivebeamlength=distancebetweenthepointwheretheloadisappliedandthecenterofthestraingage(m).
∙b=beamwidth(m).
∙t=beamthickness(m).
Youcanfindthestressfromtheappliedforceandbeamgeometry,asgivenbyequation1,andmeasurethestrainwithastraingage.Conveniently,arelationshipexistsbetweenthetwo.Themodulusofelasticity(E)isanindexofthestiffnessofthematerial.Whenaload(thatis,force)isappliedtometalsuchasanaluminumalloyorsteel,thestrainofthematerialchangeslinearlyasafunctionofthestressoveracertain,usuallysmall,range.Withinthisrange,thebeamexhibitselasticdeformation(thatis,elasticorreversiblestrain).Whenthedeformationisnotpermanent,itiscalledelasticdeformation.Thatis,whenaforceisapplied,thebeamwillbenddownwardandelongate.Whentheforceisremoved,thebeamwillreturntoitsoriginalshape.Themodulusofelasticity(E)istheratioofstresstoelasticstrainandhasunitsofN/m2:
E=
(2)
Forthislab,strainwillbemeasuredbyastraingagebondedtothetopsurfaceofabeam.Byapplyingaknownload,thestressiscalculatedusingEquati
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Stress and Strain