焊接车身点焊质量检验表的制作及检测试验

Spotweldsarethedominantjoiningmethodintheautomotiveassemblyprocess.Astheautomatedassemblyprocessisnotperfect,somespotweldsmaybeabsentwhenthevehicleleavestheassemblyline.Furthermore,spotweldsarehighlysusceptibletofatigue,sothatasubstantialnumbermayfailduringthevehiclelifetime.目前的汽车自动化装配生产线上，点焊焊接作为白车身最主要的焊接方式，其产生的焊点与车身的抗疲劳强度息息相关，如果通过有效的工艺手段及检测手段来保证焊点的质量，将直接影响整车生产出来后的使用寿命。Thescopeofthispaperistwofold.First,theimpact影响ofspotweldqualityanddesignonavehicle’sfunctionalperformanceisreviewed,addressingstrength强度andstiffness硬度,NVHanddurability耐久.TheoverviewbrieflycoversbothexperimentaltestsandpredictiveFiniteElement(FE)modelingapproaches有限元建模分析,explainsthecomplexityofaspotwelddesignproblemanddiscussesoptimizationstrategies最佳的策略.Second,anindustrialrobustnessstudyispresentedthatassesses评估theeffectofspotweldfailureondynamicvehiclecharacteristics.Damagedmodelsaregeneratedautomatically,bybreakingasubsetofthevehicle’sspotwelds,usinga(weighted)-uniformselectionprobability.MonteCarlosimulationsarethenusedtoassessthescatterondynamicvehiclecharacteristics.TheroleofComputer-AidedEngineering(CAE)intheautomotiveindustryisrapidlyincreasing.Functionalperformances(NVH,durability,...)arefine-tunedonthebasisofnumericalpredictions,sothattheexpensivephysicalprototypingphasecanbeshortenedconsiderably.Traditionally,optimizingavehiclebodystartswithimprovingthefundamentaltorsionandbendingfrequency.Thesedynamiccharacteristicsshouldberobusttofailureofspotweldconnections,thousandsofwhicharepresentinatypicalvehiclebody.Thefirstpartofthispaperoverviewstheuseofspotweldsintheautomotiveindustry.Section1dealswith涉及theresistancespotweldingprocedureandtypicalperformancesofspotwelds.Section2describessmall-scaleexperimentsandreal-lifetestingofspotweldcharacteristicsintermsofstrengthandstiffness,NVHandfatiguelife,andhighlightsthecomplexityofspotweld(layout)design.Section3describesaselectionofFiniteElementmodelsthatareusedtopredictaspotweld’sfunctionalperformancewithnumericalsimulations,andaddressesthebenefitsanddifficultiesofoptimizationonthebasisofFEmodels.Duringthevehiclelifetime,manufacturinginaccuracies不一致性,minoraccidents极小的意外的情况andfatiguefailures疲劳破话mayresultin导致deterioration质量衰退orevenabsence脱落ofasubstantialnumberofspotweldconnections.Also,inaCADmodeltransferredtoaCAEdepartment,somespotweldsmightbeomittedorforgotten.Thesecondpartofthispaperpresentsanapproachtoassesstherobustnessofdynamicvehiclecharacteristicstothisbreakageorabsence.第二部分以较为接近实际车辆的方式对以上问题点进行评定Automatedprocedureshavebeendeveloped,tobreakanumberofspotweldelementswithhigheststrainenergyinthenominal(undamaged)model,andalsotorandomlybreakanumberofwelds,eitherwithauniformprobabilityorwithaweighted-uniformprobability.ThepresentedapplicationallowsperformingMonteCarlosimulationstoassesstheeffectofrandomspotweldfailureonthedynamicvehiclecharacteristics.Section4explainsboththeinputfilecreationroutinesandtheprocessflowoftherequiredcomputations.KeyresultsaregiveninSection5.Duetotheappliedpressurebytheelectrodesduringthewelding,thethicknessofthenuggetisoftenlessthanthethicknessofthetwometalsheets.Thisso-callednuggetindentationistypicallynotsignificantforplatethicknessupto1mm,butismorepronouncedwhenthickplatesareassembled.Stressconcentration应力集中mayoccurattheedgeswhereachangeofthicknesstakesplace,whichmayresultincrackinitiation[3].Furthermore,thetransientheatingandcoolingresultsinhardeningofthematerial,andapre-stressmayremainaftercooling.剪力试验：拉力试验：Despitethedifficultiesaddressedabove,anumberofspotweldoptimizationapplicationshavebeenreportedliterature.Asimpleclampedplatemodelwithtwospotweldsisinvestigatedin[8],withtheaimoffindingtheitivityanalysisresults.Onecanenhancecomponentsscanbeparameterizedintheinputfile,andoutputmericalOptimizationStrategiesInSection2.4ithasbeenexplainedthatuncertaintiesonalevelofspotweldpositionanqualitymakeitinfeasibletoverifyalldesignoptionsonexpensivephysicalprototypesthattakesubstantialtimetomanufacture.Optimizationsinanumericalmodelingphasearemuchfasterandcheaper,andalsodecreasethelevelofcomplexityoftheproblem.ThelinearFiniteElementmodelsareasimplifiedrepresentationoftheactualproduct,resultingfromatrade-offbetweenaccuraterepresentationandfastcomputation.Manylocaleffectssuchasgeometricalirregularities,residualstresses,materialinhomogeneitiesanddefectsduetotheweldingprocess,arenottakenintoaccountbyFiniteElementmodelling.Furthermore,whereasspotweldsinaphysicalstructurecanbedeterioratedorpartly-broken,thespotweldsinthemodelingphasearediscrete:aspotweldisplacedatalocationornot.Giventhecomplexityofthedeterministicproblemitself,theparameteruncertaintyandvariabilitytypicallyneedstobeomittedfromthemodelsaswell.Probabilisticfatiguelifeassessmentstudieshavebeenperformed[9],butintegrationofparametervariabilityinanoptimizationframeworkoftenexceedscomputationaltimelimits.Evenwiththesesimplifications,thenumberofdesignparametersremainshuge:thenumberofspotwelds,theirtopology,locations,dimensions,materialproperties,...remainasdesignparameters.Emodelingphase,anytypeofindustrialspotweldoptim