某轿车白车身刚度、强度及模态有限元分析(2)

某轿车白车身刚度、强度及模态有限元分析重庆大学硕士学位论文(专业学位)学生姓名：李金龙指导教师：严波教授兼职导师：周建文高工学位类别：工程硕士（车辆工程领域）重庆大学汽车工程学院二O一五年五月FiniteElementAnalysisofStiffness,StrengthandModeofABody-in-whiteAThesisSubmittedtoChongqingUniversityinPartialFulfillmentoftheRequirementfortheProfessionalDegreeByLiJinlongSupervisedbyProf.YanBoAssistantSupervisedbyZhouJinwenSpecialty:ME(VehicleEngineeringField)CollegeofAutomotiveEngineeringofChongqingUniversity,Chongqing,ChinaMay,2015中文摘要I摘要白车身结构的优良直接影响汽车的安全性、舒适性和耐久性，车身结构设计需同时满足刚度、强度和固有频率的要求。本论文以某轿车白车身为研究对象，利用有限元方法模拟研究该白车身结构的刚度、强度和动力特性。主要研究工作如下：首先建立轿车白车身结构的力学简化模型，进而利用有限元前处理软件HYPERMESH建立三维有限元模型，包括网格划分、连接关系定义、创建并赋予材料属性等。利用NASTRAN有限元软件模拟计算该白车身结构的弯曲刚度和扭转刚度，同时利用试验测量该车身的弯曲刚度和扭转刚度。数值模拟和试验结果的比较表明，两者结果一致，验证了有限元模型的正确性。针对制动、转弯、单轮悬空等典型工况，采用有限元方法对白车身结构进行线性分析，得到车身结构的应力分布。为了更加准确地分析车身顶盖的应力分布，考虑车身顶盖构件之间的接触及材料非线性，对顶盖在雪压作用下的应力进行局部分析。最后，对该白车身结构的自由模态进行有限元分析，得到其低阶模态和固有频率。将计算所得结果与车身结构所受路面激励频率及发动机怠速频率进行比较，结果表明，该轿车车身结构的固有频率避开了共振频率，模态分布合理。本论文工作为该轿车车身结构的设计及进一步的优化提供了参考，具有重要的实际意义。关键词：有限元分析，白车身，刚度，强度，模态重庆大学硕士学位论文II英文摘要IIIABSTRACTThebody-in-whitestructuredirectlyaffectsthesafety,comfortanddurabilityofthevehicle,sowhetherthebodystructurehasgoodpropertiesisofgreatimportance.Thispapertakesthebody-in-whitestructureofacertaintypeastheresearchobject,presentsthefiniteelementmethodofhowtostudythestiffness,strengthanddynamiccharacteristicsofthebodystructure.Themainresearchworkisasfollows:Firstly,webuiltthesimplifiedmodelofthebody-in-whitestructurewiththeFEAsoftware,whichincludedthegenerationoffiniteelementmesh,thedefinitionofconnectionrelations,thedefinitionofmaterialproperties,etc.Secondly,basedontheabovemodel,wecalculatedthetorsionstiffnessandthebendingstiffnessofthebody-in-whitestructure.Meanwhile,wealsomeasuredthesamestiffnessofthebodystructurebythetest.Andthecomparisonbetweenthesimulationandthetestpresents,thetworesultsareofgoodconsistency,whichverifiesthecorrectnessofthefiniteelementmodel.Thirdly,wecalculatedthestressdistributionofbody-in-whitestructureundersometypicalworkingcondition.Inordertogetamoreaccurateanalysisoftheroof,wecarriedoutalocalstressanalysiswiththeconsiderationofthecontactbetweenrelevantcomponentsandthenonlinearityofmaterials.Theresultsshowthatthestrengthofthebody-in-whitestructuresatisfiesthedesignrequirements.Atlast,wecarriedouttheanalysisofthefreemodalofthebody-in-whitestructure,andgotthelow-ordermodalandnaturalfrequency,whichshowsthatthenaturalfrequencyofthebodystructuregetridoftheengineidlingfrequencyandtheresonancefrequency,andthemodaldistributionisreasonable.Theworkpresentedbythispaperisofvaluablereferenceforthedesignandtheoptimizationofbodystructure,whichhasimportantpracticalsignificance.Keywords:thefiniteelementanalysis,body-in-white,stiffness,strength,modal重庆大学硕士学位论文IV目录V目录中文摘要..........................................................................................................................................I英文摘要.......................................................................................................................................III1绪论......................................................................................................................................11.1工程背景及意义...................................................................................................................11.2国内外研究现状...................................................................................................................21.3本论文主要研究内容...........................................................................................................42有限单元方法的基本理论及软件介绍.................................................................72.1有限单元法的基本理论.......................................................................................................72.1.1有限单元法的基本思路............................................................................................72.1.2有限单元法的求解步骤............................................................................................82.2前后处理及有限元软件简介...............................................................................................92.2.1Hypermesh软件..........................................................................................................92.2.2Nastran软件..............................................................................................................102.2.3Ls-Dyna软件............................................................................................................112.3本章小结.............................................................................................................................113白车身有限元模型的建立.........................................................................................133.1引言......................................................................................................................................133.2几何模型修复......................................................................................................................133.3网格划分规范..............................................................................