【作者】 张迎滨；

【导师】 张建润； 朱壮瑞；

【作者基本信息】 东南大学 ， 车辆工程， 2004， 硕士

【摘要】 现代生活中,汽车在人们生活中的地位越来越重要。一个国家的汽车制造业的水平,在很大程度上也反映了其科技发展水平。许多发达国家汽车的普及已经达到了很高的程度。车身是汽车的三大总成之一,它不仅要有漂亮的整体视觉效果、足够的空间、流畅的外形曲线,更重要的是要有优越的性能。因此车身结构的设计与改进在汽车的设计中占有很重要地位。本论文立题来源江苏省科委“十五”重大科技攻关项目“南京依维柯A40新客车数字化车身动态优化与系统” 。以南京跃进汽车集团依维柯A40新客车为对象,应用数值分析和优化设计等先进技术,通过车身造型、详细有限元建模、动态试验及分析、结构优化、灵敏度分析等数字化产品设计开发技术,完成新客车车身动态优化分析。其主要内容包括:白车身的动力学建模(1) 根据白车身总成及零件装配关系建立了白车身三维实体模型。(2) 基于CATIA的CAD三维实体模型,在有限元分析软件ANSYS中经过曲面和曲线的修改、曲面重构、结构的合理简化,建立了各零部件的详细有限元模型。(3) 基于零部件及分总成的模态试验结果,对有限元总成装配模型建模精度较高的单层板结构、环形截面梁单元BEAM188和节点耦合三种方式进行比较。以精度较高的单层板结构来模拟点焊结构,以节点耦合来模拟螺栓联接结构。以能够精确反映车身冲压部件结构特性的四边形壳单元SHELL63为主,建立了各分总成详细有限元模型和由875个构件组成的精确白车身结构的有限元模型。其单元数量级在十万以上,为国内同行业领先水平。分总成及零部件模态试验及动力建模方法比较设计了乘客门脚踏板分总成及零件的模态试验。通过试验测得了分总成及零件的质量和模态特征,并与虚拟环境中的谐响应计算结果进行对比。指出了在大型有限元模型总成装配时对密集焊点较为精确的模拟方法。3.白车身结构分析(1)在虚拟环境下,模拟了白车身在静态扭转、静态弯曲、弯扭联合等典型工况。并得到了该工况下的应力分布和变形。通过计算得到的车身局部应力集中区与该车在跑车试验中所发现的危险部位统计数据基本吻合。(2)完成了虚拟环境中白车身的模态分析。通过对白车身的模态分析,获得了车身结构固有的振动特性,并找出了车身结构在动态激励时的薄弱环节。对车身结构的改进具有指导意义。(3)对比了车身与车架三种联接方式对车身侧偏刚度的影响。以螺栓联接部位耦合节点五个自由度对刚性联接方式进行模拟。以弹簧阻尼单元COMBIN14对柔性联接方式进行模拟。得到了在不同联接方式下车身承受侧向加速度时的应力和车身变形的变化情况,对生产实践具有指导意义。4.乘客门脚踏板分总成的灵敏度分析及优化设计本文的优化设计部分,以侧围脚踏板分总成为对象,通过动态敏度分析的方法,说明了车身结构优化设计的原理和方法。通过灵敏度分析,找出了在满足状态变量的条件下,对结构总重量影响较大的设计变量及其排列顺序,为结构优化提供了正确的方向。更多还原

【Abstract】 The effect of car is more and more important to modern life. The development of science and technology can be seen from manufacturing of vehicle. The degree of popularization of vehicle has been very high in some developed country. Car body is one of the three assembly of vehicle. It should be finery , wide enough , clipper-built, and the excellent capability is more important. So the improvement of vehicle structure design is very important.This thesis is originated from project “Dynamic Optimal Design and System of New Numerical Car Body A40 Nanjing Iveco”, which is the ten five-year industry item of the tackling key problem of Jiangsu province. In this paper, the finite element model of body in-white is completed. test and analysis of the static and dynamic properties, sensitivity analysis, and optimization of assembly are completed too. The main contents in this paper include:Build the dynamic model of an body in-whiteThe three dimension CAD model of the body in-white is created based on connection property between assembly and part.Based on the CAD model, the particular finite element model of parts are created in ANSYS by modifying of the curve and surface and predigestion of structure.Based on model test of the assembly and part, the precision of the three methods are compared. Simulated the spot welding structure by monolayer board, the screw joint structure by node coupling. Created the particular finite element model of assemblys and particular finite element model of body in-white which is made of 875 components in which the element are a type of quadrilateral element SHELL63 mainly. The degree of element quantity is above one hundred thousands which keep ahead natively. Model test and comparing of modeling method of the assembly and partDesign the modal test of the footplate assembly and part. The mass and modal characteristics are got through the test. Compared results of test and answer in harmony in computer. These dates have really revealed the accurate method for simulation in great finite element model when spot welding is dense.Analysis of the body in-white structureSome working conditions of body in-white such as bending and torsion of static analysis in computer are simulated in this paper. The characteristics of stress and deformation of body are got. These dates accorded with the statistical result of examination.The model analysis of body in-white are made in ANSYS. By the results of modal analysis of the body in-white, the body’s natural dynamic features are got in the paper, and located some weakness of the structure. It has positive impacts on the improvement of bus body design.Through the contrast of effect to body sideward stiffness in three ways. Simulated rigid way with coupling five degree of freedom of node, the flexible way with Spring-Damper element COMBIN14. The characteristics of stress and deformation of body are got when sideward acceleration is supported in three ways. <WP=6>The sensitivity analysis and optimization of assemblyThe paper also narrated the principle and ways of bus body structural optimization. By gradient tools, it fond some design variables that affect the total weight of structure more than that of others and arranged the order of these variables according to the effects in state conditions, which pointed out the correct direction for bus body design optimization.更多还原