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1JURNALMEKANIKALDECEMBER2008,NO26,768576STRESSANALYSISOFHEAVYDUTYTRUCKCHASSISASAPRELIMINARYDATAFORITSFATIGUELIFEPREDICTIONUSINGFEMROSLANABDRAHMAN,MOHDNASIRTAMIN,OJOKURDIFACULTYOFMECHANICALENGINEERING,UNIVERSITITEKNOLOGIMALAYSIA,ABSTRACTTHISPAPERPRESENTSTHESTRESSANALYSISOFHEAVYDUTYTRUCKCHASSISTHESTRESSANALYSISISIMPORTANTINFATIGUESTUDYANDLIFEPREDICTIONOFCOMPONENTSTODETERMINETHECRITICALPOINTWHICHHASTHEHIGHESTSTRESSTHEANALYSISWASDONEFORATRUCKMODELBYUTILIZINGACOMMERCIALFINITEELEMENTPACKAGEDABAQUSTHEMODELHASALENGTHOF1235MANDWIDTHOF245MTHEMATERIALOFCHASSISISASTMLOWALLOYSTEELA710CCLASS3WITH552MPAOFYIELDSTRENGTHAND620MPAOFTENSILESTRENGTHTHERESULTSHOWSTHATTHECRITICALPOINTOFSTRESSOCCURREDATTHEOPENINGOFCHASSISWHICHISINCONTACTWITHTHEBOLTTHESTRESSMAGNITUDEOFCRITICALPOINTIS3869MPATHISCRITICALPOINTISANINITIALTOPROBABLEFAILURESINCEFATIGUEFAILURESTARTEDFROMTHEHIGHESTSTRESSPOINTKEYWORDSTRESSANALYSIS,FATIGUELIFEPREDICTION,TRUCKCHASSIS10INTRODUCTIONTHEAGEOFMANYTRUCKCHASSISINMALAYSIAAREOFMORETHAN20YEARSANDTHEREISALWAYSAQUESTIONARISINGWHETHERTHECHASSISISSTILLSAFETOUSETHUS,FATIGUESTUDYANDLIFEPREDICTIONONTHECHASSISISNECESSARYINORDERTOVERIFYTHESAFETYOFTHISCHASSISDURINGITSOPERATIONSTRESSANALYSISUSINGFINITEELEMENTMETHODFEMCANBEUSEDTOLOCATETHECRITICALPOINTWHICHHASTHEHIGHESTSTRESSTHISCRITICALPOINTISONEOFTHEFACTORSTHATMAYCAUSETHEFATIGUEFAILURETHEMAGNITUDEOFTHESTRESSCANBEUSEDTOPREDICTTHELIFESPANOFTHETRUCKCHASSISTHEACCURACYOFPREDICTIONLIFEOFTRUCKCHASSISISDEPENDINGONTHERESULTOFITSSTRESSANALYSISTHEMOREACCURATERESULTOFSTRESSANALYSISTHEMOREVALIDTHEPREDICTEDLIFEOFOBJECTINTHISSTUDY,THESTRESSANALYSISISACCOMPLISHEDBYTHECOMMERCIALFINITEELEMENTPACKAGEDABAQUSTHEAUTOMOTIVEINDUSTRYVEHICLESANDCOMPONENTSREPRESENTSASTRATEGICANDIMPORTANTBUSINESSSECTORINMALAYSIAWITHTHEEVENTUALTRADELIBERALIZATIONOFASEANFREETRADEAREAAFTA,LOCALAUTOMOTIVEMANUFACTURERSANDVENDORSSHALLREQUIRECARSANDCOMPONENTSOFWORLDCLASSSTANDARDNOISEANDVIBRATIONAREKEYELEMENTSINSUCHSTANDARDTHEAUTOMOTIVEINDUSTRYINMALAYSIAISMUCHRELYINGONFOREIGNTECHNOLOGYTRUCKCHASSIS,WHICHISIMPORTANTSTRUCTUREOFLIGHTWEIGHTCOMMERCIALVEHICLE,ISMOSTLYDESIGNEDANDIMPORTEDFROMFOREIGNCOUNTRYINORDERTOCHANGETHISTREND,ITISNECESSARYTODEVELOPANDBUILTMALAYSIANOWNCHASSISDESIGNSTUDYANDRESEARCHONTRUCKCHASSISISTHUSREQUIREDTOACHIEVETHISGOALTHECHASSISOFTRUCKSISTHEBACKBONEOFVEHICLESANDINTEGRATESTHEMAINTRUCK2COMPONENTSYSTEMSSUCHASTHEAXLES,SUSPENSION,POWERTRAIN,CABANDTRAILERTHETRUCKCHASSISISUSUALLYLOADEDBYSTATIC,DYNAMICANDALSOCYCLICLOADINGSTATICLOADINGCOMESFROMTHEWEIGHTOFCABIN,ITSCONTENTANDPASSENGERSTHEMOVEMENTOFTRUCKAFFECTSADYNAMICLOADINGTOTHECHASSISTHEVIBRATIONOFENGINESANDTHEROUGHNESSOFROADGIVEACYCLICLOADINGTHEEXISTINGTRUCKCHASSISDESIGNISNORMALLYDESIGNEDBASEDONSTATICANALYSISTHEEMPHASISOFDESIGNISONTHESTRENGTHOFSTRUCTURETOSUPPORTTHELOADINGPLACEDUPONITHOWEVER,THETRUCKCHASSISHASBEENLOADEDBYCOMPLEXTYPEOFLOADS,INCLUDINGSTATIC,DYNAMICSANDFATIGUEASPECTSITISESTIMATEDTHATFATIGUEISRESPONSIBLEFOR85TO90OFALLSTRUCTURALFAILURESTHEKNOWLEDGEOFDYNAMICANDFATIGUEBEHAVIOROFTRUCKCHASSISINSUCHENVIRONMENTISTHUSIMPORTANTSOTHATTHEMOUNTINGPOINTOFTHECOMPONENTSLIKEENGINE,SUSPENSION,TRANSMISSIONANDMORECANBEDETERMINEDANDOPTIMIZEDMANYRESEARCHERSCARRIEDOUTSTUDYONTRUCKCHASSISKARAOGLUANDKURALAYINVESTIGATEDSTRESSANALYSISOFATRUCKCHASSISWITHRIVETEDJOINTSUSINGFEMNUMERICALRESULTSSHOWEDTHATSTRESSESONTHESIDEMEMBERCANBEREDUCEDBYINCREASINGTHESIDEMEMBERTHICKNESSLOCALLYIFTHETHICKNESSCHANGEISNOTPOSSIBLE,INCREASINGTHECONNECTIONPLATELENGTHMAYBEAGOODALTERNATIVEFERMERETALINVESTIGATEDTHEFATIGUELIFEOFVOLVOS80BIFUELUSINGMSC/FATIGUECONLEANDCHUDIDRESEARCHABOUTFATIGUEANALYSISANDTHELOCALSTRESSSTRAINAPPROACHINCOMPLEXVEHICULARSTRUCTURESSTRUCTURALOPTIMIZATIONOFAUTOMOTIVECOMPONENTSAPPLIEDTODURABILITYPROBLEMSHASBEENINVESTIGATEDBYFERREIRAETALFERMRANDSVENSSONSTUDIEDONINDUSTRIALEXPERIENCESOFFEBASEDFATIGUELIFEPREDICTIONSOFWELDEDAUTOMOTIVESTRUCTURESFILHOETALHAVEINVESTIGATEDANDOPTIMIZEDACHASSISDESIGNFORANOFFROADVEHICLEWITHTHEAPPROPRIATEDYNAMICANDSTRUCTURALBEHAVIOR,TAKINGINTOACCOUNTTHEASPECTSRELATIVETOTHEECONOMICALVIABILITYOFANINITIALSMALLSCALEPRODUCTIONTHEDESIGNOFANOFFROADVEHICLECHASSISISOPTIMIZEDBYINCREASINGTHETORSIONALSTIFFNESS,MAINTENANCEOFCENTEROFGRAVITY,TOTALWEIGHTOFSTRUCTUREANDSIMPLERGEOMETRYFORREDUCTIONOFPRODUCTIONCOSTTHEINTEGRATIONOFCOMPUTERAIDEDDESIGNANDENGINEERINGSOFTWARECODESPRO/ENGINEER,ADAMS,ANDANSYSTOSIMULATETHEEFFECTOFDESIGNCHANGESTOTHETRUCKFRAMEHASBEENSTUDIEDBYCOSMEETALCHIEWANICHAKORNETALINVESTIGATEDTHEBEHAVIOROFATRUSSBRIDGE,WHEREANFRPDECKREPLACEDANOLDDETERIORATEDCONCRETEDECK,USINGEXPERIMENTALLYVALIDATEDFINITEELEMENTFEMODELSNUMERICALRESULTSSHOWTHATTHEFATIGUELIFEOFTHEBRIDGEAFTERREHABILITATIONWOULDBEDOUBLEDCOMPAREDTOPREREHABILITATEDREINFORCEDCONCRETEDECKSYSTEMBASEDONTHEESTIMATEDTRUCKTRAFFICTHATTHEBRIDGECARRIES,STRESSRANGESOFTHEFRPDECKSYSTEMLIEINANINFINITEFATIGUELIFEREGIME,WHICHIMPLIESTHATNOFATIGUEFAILUREOFTRUSSESANDFLOORSYSTEMWOULDBEEXPECTEDANYTIMEDURINGITSSERVICELIFEYEANDMOANHAVEINVESTIGATEDTHESTATICANDFATIGUEBEHAVIOROFALUMINIUMBOXSTIFFENER/WEBFRAMECONNECTIONSUSINGFINITEELEMENTANALYSISFEATOPROVIDEACONNECTIONSOLUTIONTHATCANREDUCETHEFABRICATIONCOSTSBY3CHANGINGTHECUTTINGSHAPESONTHEWEBFRAMEANDCORRESPONDINGLYTHEWELDPROCESSMEANWHILESUFFICIENTFATIGUESTRENGTHCANBEACHIEVEDFEBASEDFATIGUEWASUSEDTOLOCATETHECRITICALPOINTOFPROBABLECRACKINITIATIONANDTOPREDICTTHELIFEINADOORHINGESYSTEMINTHISSTUDY,STRESSANALYSISOFHEAVYDUTYTRUCKCHASSISLOADEDBYSTATICFORCEWILLBEINVESTIGATEDTODETERMINETHELOCATIONOFCRITICALPOINTOFCRACKINITIATIONASAPRELIMINARYDATAFORFATIGUELIFEPREDICTIONOFTHISTRUCKCHASSIS20FINITEELEMENTANALYSISOFTRUCKCHASSIS21BASICCONCEPTOFFEMTHEFINITEELEMENTMETHODFEMISACOMPUTATIONALTECHNIQUEUSEDTOOBTAINAPPROXIMATESOLUTIONSOFBOUNDARYVALUEPROBLEMSINENGINEERINGSIMPLYSTATED,ABOUNDARYVALUEPROBLEMISAMATHEMATICALPROBLEMINWHICHONEORMOREDEPENDENTVARIABLESMUSTSATISFYADIFFERENTIALEQUATIONEVERYWHEREWITHINAKNOWNDOMAINOFINDEPENDENTVARIABLESANDSATISFYSPECIFICCONDITIONSONTHEBOUNDARYOFTHEDOMAINANUNSOPHISTICATEDDESCRIPTIONOFTHEFEMETHODISTHATITINVOLVESCUTTINGASTRUCTUREINTOSEVERALELEMENTSPIECESOFSTRUCTURE,DESCRIBINGTHEBEHAVIOROFEACHELEMENTINASIMPLEWAY,THENRECONNECTINGELEMENTSATNODESASIFNODESWEREPINSORDROPSOFGLUETHATHOLDELEMENTSTOGETHERTHISPROCESSRESULTSINASETOFSIMULTANEOUSALGEBRAICEQUATIONSINSTRESSANALYSISTHESEEQUATIONAREEQUILIBRIUMEQUATIONSOFTHENODESTHEREMAYBESEVERALHUNDREDORSEVERALTHOUSANDSUCHEQUATIONS,WHICHMEANTHATCOMPUTERIMPLEMENTATIONISMANDATORY22AGENERALPROCEDUREFORFEATHEREARECERTAINCOMMONSTEPSINFORMULATINGAFINITEELEMENTANALYSISOFAPHYSICALPROBLEM,WHETHERSTRUCTURAL,FLUIDFLOW,HEATTRANSFERANDSOMEOTHERSPROBLEMTHESESTEPSAREUSUALLYEMBODIEDINCOMMERCIALFINITEELEMENTSOFTWAREPACKAGESTHEREARETHREEMAINSTEPS,NAMELYPREPROCESSING,SOLUTIONANDPOSTPROCESSINGTHEPREPROCESSINGMODELDEFINITIONSTEPISCRITICALAPERFECTLYCOMPUTEDFINITEELEMENTSOLUTIONISOFABSOLUTELYNOVALUEIFITCORRESPONDSTOTHEWRONGPROBLEMTHISSTEPINCLUDESDEFINETHEGEOMETRICDOMAINOFTHEPROBLEM,THEELEMENTTYPESTOBEUSED,THEMATERIALPROPERTIESOFTHEELEMENTS,THEGEOMETRICPROPERTIESOFTHEELEMENTSLENGTH,AREA,ANDTHELIKE,THEELEMENTCONNECTIVITYMESHTHEMODEL,THEPHYSICALCONSTRAINTSBOUNDARYCONDITIONSANDTHELOADINGSTHENEXTSTEPISSOLUTION,INTHISSTEPTHEGOVERNINGALGEBRAICEQUATIONSINMATRIXFORMANDCOMPUTESTHEUNKNOWNVALUESOFTHEPRIMARYFIELDVARIABLESAREASSEMBLEDTHECOMPUTEDRESULTSARETHENUSEDBYBACKSUBSTITUTIONTODETERMINEADDITIONAL,DERIVEDVARIABLES,SUCHASREACTIONFORCES,ELEMENTSTRESSESANDHEATFLOWACTUALLYTHEFEATURESINTHISSTEPSUCHASMATRIXMANIPULATION,NUMERICALINTEGRATIONANDEQUATIONSOLVINGARECARRIEDOUTAUTOMATICALLYBYCOMMERCIALSOFTWARETHEFINALSTEPISPOSTPROCESSING,THEANALYSISANDEVALUATIONOFTHERESULTISCONDUCTEDINTHISSTEPEXAMPLESOFOPERATIONSTHATCANBEACCOMPLISHEDINCLUDE4SORTELEMENTSTRESSESINORDEROFMAGNITUDE,CHECKEQUILIBRIUM,CALCULATEFACTORSOFSAFETY,PLOTDEFORMEDSTRUCTURALSHAPE,ANIMATEDYNAMICMODELBEHAVIORANDPRODUCECOLORCODEDTEMPERATUREPLOTSTHELARGESOFTWAREHASAPREPROCESSORANDPOSTPROCESSORTOACCOMPANYTHEANALYSISPORTIONANDTHEBOTHPROCESSORCANCOMMUNICATEWITHTHEOTHERLARGEPROGRAMSSPECIFICPROCEDURESOFPREANDPOSTAREDIFFERENTDEPENDENTUPONTHEPROGRAM23TRUCKDEFINITIONANDCLASSIFICATIONGENERALLY,TRUCKISANYOFVARIOUSHEAVYMOTORVEHICLESDESIGNEDFORCARRYINGORPULLINGLOADSOTHERDEFINITIONOFTHETRUCKISANAUTOMOTIVEVEHICLESUITABLEFORHAULINGSOMEOTHERDEFINITIONAREVARIEDDEPENDINGONTHETYPEOFTRUCK,SUCHASDUMPTRUCKISATRUCKWHOSECONTENTSCANBEEMPTIEDWITHOUTHANDLING；THEFRONTENDOFTHEPLATFORMCANBEPNEUMATICALLYRAISEDSOTHATTHELOADISDISCHARGEDBYGRAVITYTHEREARETWOCLASSIFICATIONSMOSTAPPLICABLETORECREATIONALVEHICLETOWTRUCKSTHEFIRSTONEISTHEWEIGHTCLASSES,ASDEFINEDBYTHEUSGOVERNMENT,RANGINGFROMCLASS1TOCLASS8ASLISTEDINTABLE1ANDTABLE2THESECONDISCLASSIFIEDINTOABROADERCATEGORYLIGHTDUTYTRUCKMEDIUMDUTYTRUCKHEAVYDUTYTRUCK24MODELOFTRUCKCHASSISTHEMODELISDEPICTEDINFIGURE2THEMODELHASLENGTHOF1235MANDWIDTHOF245MTHEMATERIALOFCHASSISISASTMLOWALLOYSTEELA710CCLASS3WITH552MPAOFYIELDSTRENGTHAND620MPAOFTENSILESTRENGTHTHEOTHERPROPERTIESOFCHASSISMATERIALARETABULATED25LOADINGTHETRUCKCHASSISMODELISLOADEDBYSTATICFORCESFROMTHETRUCKBODYANDCARGOFORTHISMODEL,THEMAXIMUMLOADEDWEIGHTOFTRUCKPLUSCARGOIS36000KGTHELOADISASSUMEDASAUNIFORMPRESSUREOBTAINEDFROMTHEMAXIMUMLOADEDWEIGHTDIVIDEDBYTHETOTALCONTACTAREABETWEENCARGOANDUPPERSURFACEOFCHASSIS26BOUNDARYCONDITIONSTHEREARE3BOUNDARYCONDITIONSBCOFMODEL；THEFIRSTBCISAPPLIEDINFRONTOFTHECHASSIS,THESECONDANDTHETHIRDBCAREAPPLIEDINREAROFCHASSISTHEYARESHOWNTHETYPEOFBC1ISPINNEDTHEDISPLACEMENTISNOTALLOWEDINALLAXESANDTHEROTATIONISALLOWEDINALLAXESTHATREPRESENTTHECONTACTCONDITIONBETWEENCHASSISANDCABOFTRUCKASSHOWNTHEBC2REPRESENTSTHECONTACTBETWEENCHASSISANDUPPERSIDEOFSPRINGTHATTRANSFERLOADEDWEIGHTOFCARGOANDCHASSISTOAXLETHECONTACTCONDITIONOFBC2INTHEOBJECTISSHOWNINTHEBC2,THEDISPLACEMENTONLYOCCURREDINAXIS2ANDTHEROTATIONRESPECTTOALLAXESISZEROINTHEPOSITIONWHERETHEBC3APPLIED,THEREISACONTACTBETWEENINSIDESURFACEOFOPENINGCHASSISANDOUTSIDESURFACEOFBOLTINABAQUS,THISCONTACTISCALLEDINTERACTIONINTHISCASE,THETYPEOFTHEINTERACTIONISFRICTIONLESSSURFACETOSURFACECONTACTINTHEBC3,THEDISPLACEMENTANDTHEROTATIONISZEROINALLAXESONALLOFBOLT’SBODYTHISCONDITIONISCALLEDFIXEDCONSTRAINTHEBOLTIN
