全文预览已结束
下载本文档
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
ExperimentalanalysisofacompositeautomotivesuspensionarmM.PINFOLDandG.CALVERT(UniversityofWarwick/RoverGroupGaydon,UK)Received11November1992;revised26March1993Inapplicationswhereweightsavingandpartsintegrationcanbeachieved,theRoverGrouphasbeeninvestigatingthedesignandmanufactureofcomponentsfromcompositematerials.Themethodsusedinthedifferentstepsinthedesign-to-manufacturecycleinthehighvolumeautomotiveindustryarerelativelywellknownforasteelcomponent,butarenotsowellestablishedforacompositecomponent.Adesignmethodologyforcompositeshasbeenemerginginwhichaprincipalprocedureisdesignanalysis.Oneofthemostestablishedmethodsofanalysisisthatusingthefiniteelementtechnique,andthisisbeingsupplementedwithexperimentaltestsonprototypesusingphotoelasticanalysisandstresspat-ternanalysisbythermalemission,coupledwithconventionalstraingaugemoni-toring.Littleworkhasbeenundertakentocorrelatetheresultsobtainedfromthesedifferenttestmethodsandtocomparetheresultswithmeasurementsmadeonanactualcomponent.Thispaperpresentssomeoftheworkundertakenconcerningtheanalysisandtestingofacompositeautomotivesuspensionarm.Theresultsobtainedfromthethreedifferentanalysistechniquesarecomparedwithexperi-mentaltestresults,andtheiraccuracyisdiscussed.Keywords:autmotivesuspensionarm;stressanalysis;finiteelementmethod;photoelasticanalysis;SPATE;straingauges;sheetmouldingcompoundSolanddeWildestatethatcompositematerialshavebeenusedincreasinglyasstructuralmaterials.Areasonforthis.,isthatcompositematerialshavehighstrengthtoweightandhighstiffnesstoweightratioswhichcansignificantlyreducetheweightofastructure.Perhapsthemostimportantfeatureofcompositematerialsisthattheirmechanicalp:opertiescanbetailoredtomeetaspecificcriterion.However,Johnsonetal?suggestthatcompositedesign,analysisandfabricationtechnologymustundergomajordevelopmentsandsuccessfuldemonstrationsbeforesignificantstructuralcomponentswillbeincorporatedinproductionautomobilesandtrucks.Compositematerialshavetocompetewithsteelwithintheengineeringenvironment.WithintheautomotiveindustrythisrequiresacertainamountoftechnologytransferfromplacessuchastheAdvancedTechnologyCentreattheUniversityofWarwick,whichworkwithmaterialmanufacturersandautomotiveengineerstoenableunderstandingaboutthesematerialsasanalter-nativetothetraditionalmaterialssuchassteel.Ifcom-positesaretocompetewithtraditionalmaterialsinarealsense,thenautomotivedesignersneedtobefullyaware0010-4361/94/010059-05oftheirstrengthsandlimitationssothattheycanbeoneofperhapsmanyoptionsconsideredattheconceptstageofthedesign.Forthistohappenautomotiveengineersneedtocatchuponthetechniquesofdesigning,testingandmanufacturingcomponentsfromcomposites.Thiswillincludeunderstandinghowvariousmethodssuchasfiniteelement(FE)analysis,stresspatternanalysisbythermalemission(SPATE)andphotoelasticanalysiscanbeappliedtocompositecomponentsintheirdesignanddevelopment.Thusfarlittleworkappearstohavebeenundertakentostudywhethertheresultsobtainedfromthesedifferentanalysismethodscorrelatewithoneanotherorwithactualexperimentalresultsobtainedfromtestingarealcomponent.Inordertostudytheapplicationandcorre-lationofthedifferentanalysismethodstocompositematerials,acompositecomponent-anautomotivelowersuspensionarm-wasmanufactured.Thiscom-positecomponentwasanalysedbythethreemethodsdescribedaboveandalsotestedunderrealisticloadingconditions,withexperimentalresultsbeingobtainedfromstraingauges.1994Butterworth-HeinemannktdCOMPOSITES.VOLUME25.NUMBER1.199459,BallJointHousingFig.1ThecompositesuspensionarmDESIGNTheexistingsteellowersuspensionarmconsistsofninepiecesweldedtogetherwhilstthere-designedcompositecomponent-whichcanbeseeninFig.1-isasinglemouldedpart.Thematerialusedtomanufacturethesuspensionarmwasasheetmouldingcompound(SMC),comprisingapolyesterresinbondingagentwitha30%contentofrandomlyarrangedshortglassfibresandcal-ciumcarbonatefiIler.Theweightofthesteelsuspensionarmis2.53kgwhilstthere-designedSMCsuspensionarmcompletewithbushesandballjointweighs1.5kg.Thematerialpropertiesusedforthecompositesuspensionarmintheseanalyses,obtainedfromtestscarriedoutatRoversmaterialslaboratory,wereYoungsmodulus=10.5GPa,Poissonsratio=0.26anddensity=1.8x10-6kgmm-3.EXPERIMENTALTECHNIQUESPriortoundertakingexperimentalanalysisofanactualengineeringcomponent,someinitialvalidationworkwasrequiredtogainconfidenceinthetechniqueswhenappliedtosheetmouldingcompound.Therefore,fiatplates,beamsanddiscsconstructedfromSMCwereana-lysedundervariousloadingconditionsbeforeprogress-ingontothedesignedcomponent.Mostvalidationtestswerecarriedoutusingstrain-gaugedspecimenstocorrelatewiththefiniteelementanalysisresults.AlthoughitisrecognizedthatSMCisnotanisotropiematerialduetosomefibreorientationduringprocessing,forthepurposesofanalysisthemater-ialwasassumedtobeisotropic.Also,whentheactualSMCsuspensionarmwascutupandexamined,signifi-cantfibredistributionwasobservedintheribs.Itisfeltthatthecorrelationbetweentheexperimentalandanaly-sisresultsvalidatedthisassumptioninthecaseofthisparticularcomponent.StraingaugetestsBeforeundertakingtheexperimentaltestwork,thecom-positecomponentwasmountedviaitsrubbermountingbushesontoarelativelyinfinitelystiffstructure.Itisverydifficulttocoveralloftheloadingconditionswhencon-ductingexperimentaltestsandthusaworst-casescenarioisusuallyassumed.Theworst-caseloadingconditiononsuspensioncomponentsisknownaspot-holebrake.Thisattemptstosimulatethevehiclefallingintoadeeppot-holeat30mphwiththebrakesfullyappliedatthepointofimpact.Theresultantfore/aftandlateralloadsarethencalculatedbasedontheweightandvelocityofthevehicle.Duetothelimitationsofthetestrigthefullpot-holeloadscouldnotbeappliedtothecomponent,andthusreducedloadswiththesameresultantdirectionasthepot-holeloadswereappliedandtheresultsscaled.Theloadsappliedforthefullpot-holebrakecasewere24.2kNinXand8.2kNinY,andforthereducedloadcasewere5.9kNinXand2.02kNinY-seeFig.1.Thestraingaugesusedconsistedofsixthree-axisrosettegaugesand13single-gridgauges,with2.5mmgridlengths,chosentofitintotheradiiofthecomponentinanattempttomeasurethemaximumstrain,Gaugesweresituatedneartheballjointhousing,wheretheloadswereapplied,andaroundtheradiiofthebodymountingbushes,wherethecomponentwouldbemountedtothecarsubframe.Additionalstraingaugesweresituatedonsomeofthestrengtheningribsandclosetotheanti-rollbarmountingposition.SPATEanalysisStresspatternanalysisbythermalemission(SPATE)canbeusedtodeterminethesurfacestressesofcomponentsbystudyingthesmallchangesintemperatureduetocyclicloadingconditions.SPATEequipmentcomprisesadetectorunitwithscanninghead,ananaloguesignalprocessingunitandadigitalelectronicdataunit.Thesystemworksbydetectingtheminutetemperaturechangeswhichoccurwhenastructureiscyclicallyloaded.Theinfra-reddetectorscansthestructureandcorrelatesthemeasuredoutputwithareferencesignalfromtheloadingsystem.Anelectronicdataprocessingsystemcorrelatesthedetectedstress-inducedthermalfluctuationswiththeloadingreferencesignal.Acolourcontourmapofthesumoftheprincipalstresses(cr+4)isthenplotted,togetherwithabarchartgivingactualvalues.Thiscorrelationofsignalseffectivelyeliminatesallsignalfrequenciesotherthanthosecausedbytheloadingsystem,i.e.,allambienttemperaturefluctua-tions.TheSPATEsystemhasatemperatureresolutionof0.001C,andaspatialresolutionoflessthanImm.ThistypeofanalysishasbeenshownbyanumberofauthorsTMtoalsobeapplicabletonon-isotropicmater-ialssuchascomposites,andthesmallerrors(6%)demonstratedfromsuchstudieswhencomparedwiththeoreticalorFEresultsarefelttobeduetoinaccuraciesinthematerialdataused4.Itisapparentfromthestudiesundertakenthattheuseofthermoelasticstressanalysistoevaluatestressesandstrainsinanisotropiccompositematerialsismorecomplexthanforisotropicmaterials.However,ithasbeenshownthatthetechniquecanprovidevaluablequalitativeinformationonstressdistri-bution,effectsofsurfacedefectsandcrackgrowthpredictions.Ithasalsobeendemonstratedthat,givenaccuratedetailsofmaterialpropertiesincludingexpan-sioncoefficients,quantitativeresultscanbeobtaineddependinguponthedegreeofanisotropyofthematerial.PriortoundertakingafullSPATEanalysisofthesuspen-sionarmitwasnecessarytodetermineacalibrationfactorforthematerialused.Thiscanbeachievedintwoways,eitherbyloadingadiscofthematerialincompres-sionandcomparingtheSPATEoutputwiththetheoreti-60COMPOSITES.NUMBER1.1994calsolution,orbystraingaugingdirectlyontothecomponentinanareaofevenstressdistribution,therebyobtainingadirectcomparisonwiththeSPATEoutput.Bothmethodswereusedinthiscase,butdirectcalib-rationwithstraingaugescanovercomealotoftheproblems,thusallowingsignificantinformationtobeobtainedfromtheSPATEoutput.PhotoelasticanalysisThemajorityofphotoelasticworkinvestigatingthemac-romechanicalbehaviourofcompositematerialshasbeenundertakenusingphotoelasticcoatingtechniques.Thisisdonetoavoidthecomplexitiesofconstructingaphoto-elasticmodelwithanisotropicpropertiesandthuscon-structingacompositeliketheoriginalwhichwouldloseitstransparencyandcouldnotbeanalysed.However,forcomplexfibrelay-upsthiswouldbetheonlymethodofconductingphotoelasticanalysis,andthussomeresearchhasbeenundertakeninvestigatingtheuseoftheactualcompositesj7-30.Reasonableresultshavebeenobtainedfromsuchanalyses,butwithlimitationsduetotheneces-sityfortransparencywithinthecomposite.However,thecompositecomponentconsideredinthisstudywasmanufacturedfromSMCandthematerialwasassumedtobeisotropic,thussimplifyingthecreationofaphoto-elasticmodel.Athree-dimensionalepoxyresinmodelofthesuspensionarmwasconstructedforthephotoelasticanalysis.Themodelwasthenloadedinarepresentativemanner,withscaled-downloads,andsubjectedtoastressfreezingcycle.Thisinvolvesheatingthemodeluptothemater-ialsglasstransitiontemperature,atwhichpointtheYoungsmoduluschanges,andthemodeldeformsundertheappliedloads.Themodelisthenslowlycooled,avoidinganyuneventemperaturedistributionwhichcouldresultinunwantedthermalstresses.Duringthecoolingcyclethedeformationsandstressesarelockedintothemodel.Whenviewedunderpolarizedlightthethree-dimensionalmodelisajumbleofinterferencefringes.Inordertodeterminebothmagnitudeanddirec-tionoftheprincipalstressesatanypoint,asliceisremovedandobservedunderpolarizedlight.Bycount-ingthefringesthestressesinthemodelcanbecalculatedandconvertedintoactualstressinthecomponent.Thisisdonebymeansofproportionality,betweenthemodelandcomponentmaterials,andtheloadinganddimensio-nalparameters.Thelowersuspensionarmismountedtotherestofthecarviarubbermountingbushes.Investigationswerecarriedoutastothepossibilityofmodellingthesemountingbushes.However,experimentswithsiliconandfoamrubbersshowedthattherequiredscaled-downstiffnessofthebushesduringstressfreezingatelevatedtemperaturescouldnotbemaintained.Thephotoelasticanalysisthusassumedthatthesuspensionarmwassolidlymounted.FINITEELEMENTANALYSISThecompositesuspensionarmwasmodelledusingapproximately1300oftheSTIF45ANSYSsolidele-ments.Thesuspensionarmismountedtothesubframeviarubbermountingbushes;theseweremodelledwithspringelementstorepresentthestiffnessofthebushesandtocreatearealisticloaddistributionthroughoutthecomponent.LoadswereappliedtotheFEmodelviabeamelementsattheballjoint.ThreeloadcaseswereanalysedusingtheANSYSFEsoftware.Thefirstloadcasesimulatedthefullpot-holebrakeloads.Thesecondsimulatedthereducedloadusedinthetestsduetothelimitationsofthetestrig,toenablecomparisonswiththeresultsfromtheexperimentalstraingaugeanalysis.Thesetwoloadcasesusedspringelementstosimulatethestiffnessoftherubbermountingbushes.Thethirdloadcaseagainusedthereducedloadsbutthistimeomittedthespringelements;i.e.,thesuspen-sionarmwasmodelledasbeingsolidlymounted.ThisthirdloadcasewasrequiredtocorrelatewiththeSPATEandphotoelasticanalyses.RESULTSFiniteelementanalysisAnalysisofthesuspensionarmshowedthatthemaxi-mumequivalentstressinthecomponentfortheloadcaseconsideredisveryclosetotheultimatetensilestrengthoftheproposedmaterialforthepot-holeloadingcondition,whichistheworstloadingcondition.Thismeansthatthecomponentmayneedtobemanufacturedfromadiffer-entmaterial,orthatothermaterialsneedtobeposit-ionedinareasofhighstresstostrengthenthecomponentlocally.Duetoconstraintsupontheamountofcomputerdiscspaceavailable,thenumberofelementsusedwithintheFEmodelwasrelativelylowandthusthesizeoftheelementswithintheareaoftheradiiaroundthebodymountingbusheswastoolargetodetectanylargestressconcentrations.Also,thetypesofelementusedaroundtheseareas,duetothegeometryofthecomponent,wereamixtureofbrick,wedgeandtetrahedral.Thelattershapetendstobetoostifftogivegoodresultsandisnotrecommended.Ifmoredetailedresultswererequiredintheseareas,thentheseradiiwouldhavetobemodelledingreaterdetailwithmoreandsmallerelementsintheareasofhighstressgradient.PhotoelasticanalysisTheanalysisofthephotoelasticmodelofthesuspensionarmwasundertakenassumingthatthedirectionsofthemaximumprincipalstresseslayinahorizontalplanethroughthemodelinthedirectionofthefore/aftload.Whilstthisisnotstrictlytrueinpracticeduetolocalgeometryeffectsincertainareas,theassumptiongavesufficientlyaccurateresults.Ifobviousdiscrepancieswerefoundinparticularareasthenitwaspossibletotakeslicesfromdifferentplanes.Maximumstresseswereseentooccurinthevicinityoftheballjointhousingandthebodymounts.Duetotheabilityofphotoelasticanalysistopinpointverysmallareasofhighstress,themaximumstressvaluesgivenbyphotoelasticitytendedtobehigherthanthestraingaugeresults.Forexample,maximumstresslevelsintheinternalradiusoftheleadingbodymountwerefoundtobe43MPacomparedwithaSPATEvalueof26MPa.Thisdifferencecanbeexplainedbyexamin-ingtheslicetakenthroughthephotoelasticmodelwhichshowsthatthemaximumstressonlyoccursatapositionCOMPOSITES.NUMBER1.199461Table1.Stressresults(MPa)forfullloadcon-ditionsPositionStraingaugesFEPhotoelasticBalljointhousing176165176spanning3mmandthatthestressvalueseithersideofthemaximumarearound25MPa.SPATEanalysisTheinitialSPATEscanshowedlargebandsofstressrunningacrossthemountingareasandsomeconfusionastowhethertheseareaswereintensionorcompression.Theproblemwasidentifiedasexcessivemovementinthesuspensionarmbodymountingpositionsduetodistor-tionoftherubberbushesasexperiencedinthestraingaugetests.SPATEisequippedwithamotioncompen-satordeviceifrequired,whichdeflectsthescanningmirrorsinsidethedetectorintimewiththeoscillationsofthetest-piece,therebyeliminatingthemovement.How-ever,inthisparticularcase,thegeometryanddirectionofmovementcouldnotbeeliminatedovertheentireareaatthesametime,andthusitwasnecessarytoremovetherubberbushesandtoreplacethemwithaluminiumones.TheSPATEanalysiswasrepeatedwiththesolidbushesandshowedareasofhightensilestress(26MPa)alongtheleadingedgeandaroundtheinnerradiusoftheleadingbodymountingposition.Unfortunately,noSPATEanalysiscouldbeundertakenattheballjointendofthecomponentasitwasobscuredbythelargeloadingadaptorrequiredtofitthehydraulicactuatorsupplyingthecyclicloading.COMPARISONOFRESULTSItshouldbeclarifiedthatthestressvaluesquotedinthetablesfromthestraingaugeresultswerecalculatedfromtherosettegaugestogiveavalueofmaximumprincipalstress.Thephotoelasticanalysisalsogivesmaximumprincipalstressesunlessthevaluesaretakeninboardofafreeedgeinwhichcasetheyaredifferencesinprincipalstresses(o.-o-,).SPATEanalysisgivesanoutputintheformofthesummationoftheprincipalstresses(or.+a2)whereastheFEoutputcanbeinanyformrequired(inthiscaseyonMises).Duetothegeometryofthecompo-nentandthewayinwhichtheloadswereapplied,thevaluesofor2andcr3werealwayssmall,andthusdirectcomparisonscouldbemadebetweenthedifferentanaly-sismethodswithoutfurtherconversion.Tablelcomparestheresultsobtainedforthemaximumpot-holeloadconditions.Themaximumstressvaluesalloccurattheballjointareaandcorrelateverywell.Theseresultantstressesforthestraingaugesandphotoelasti-citywerecalculatedfromtheresultsobtainedforthereducedload.Themodelstresswasmultipliedbyaload-ingfactorastheratiobetweenthefore/aftandlateralloadingremainedconstantandinthesameproportionasthefullpot-holebrakeloadappliedtothesuspensionarlTI.TheresultsoftheanalysesundertakenwithreducedTable2.Stressresults(MPa)forredTJcedloadswithmountingbushesPositionStraingaugesFEInnerradiusofbody2520mountBalljointhousing4940Table3.Stressresults
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 年产1200吨包装材料迁建项目可行性研究报告
- 年印刷塑料薄膜200吨生产项目可行性研究报告
- 高速光通信用探测器芯片研发及生产能力提升项目可行性研究报告
- 某市绿色粮食仓储建设项目可行性研究报告
- 碳纤维应用项目可行性研究报告
- 江苏省宿迁市泗阳县重点名校2024届中考试题猜想物理试卷含解析
- 江苏省徐州市部分2024年中考三模数学试题含解析
- 2024全新标准合同排版下载
- 老年专科护士的培养及使用
- 小学三年级数学两位数乘一位数计算综合考核练习题带答案
- kis迷你版操作手册
- BCP业务连续性计划
- 小学生数学六年级毕业试卷(附:试卷命题意图、参考答案及评分标准)
- 西师版(五年级下册)数学全册总复习课件
- 财务报表大全(中英文对照版)
- UML-网吧管理系统
- 普通外科Ⅰ类(清洁)切口手术围手术期预防用抗菌药物管理实施细则
- 机械搅拌澄清池设计
- WAW600B微机屏显式液压万能试验机
- 2022年全国教育科学规划课题活页.docx
- 项目保密管理制度和流程
评论
0/150
提交评论