【作者】 李佳；

【导师】 成艾国；

【作者基本信息】 湖南大学 ， 车辆工程， 2011， 硕士

【摘要】 随着汽车工业的快速发展,汽车市场的竞争也日益激烈,人们对汽车车身刚度、强度、耐久性和安全性的要求越来越高,这就需要在汽车的概念设计阶段采取快速有效的车身结构设计方法,既保证汽车的性能和质量,又能够缩短设计周期、降低开发成本。在汽车的概念设计阶段,车身整体布置和外型尺寸往往受到车型定位和造型的限制,改动余地较小;而车身关键截面和接头结构的设计余地较大,而且接头往往是车身结构中疲劳寿命的薄弱区域,所以在概念设计阶段尽早对接头区域等车身关键结构进行疲劳耐久性设计,对于提高整个车身结构设计效率有着重要意义。本文针对汽车概念设计阶段车身结构参数输入信息较少、难以建立详细完整的整车有限元模型以及无法进行传统耐久性试验等问题,提出了一种适用于概念设计阶段的基于真实接头的车身概念简化模型(简称ZJ);并完成了以ZJ为主体的整车耐久性虚拟试验模型建立、整车耐久性虚拟道路试验仿真分析以及车身关键接头结构的疲劳寿命分析和优化设计等几个方面的工作,主要的研究内容如下:(1)介绍了国内外车身结构概念设计、车身接头结构以及车身疲劳耐久性等方面的研究现状,指出在概念设计阶段尽早进行车身关键结构的耐久性设计对于缩短车身开发周期、降低开发成本以及提高产品竞争力有着重要意义。(2)提出了一种基于真实接头的车身概念简化模型:在新车型的概念设计阶段,根据车身总布置尺寸要求,从企业的车身关键截面特性数据库和车身真实接头数据库中调用基型车参数,建立具有真实接头并辅以梁单元和大尺寸壳单元组成的车身简化模型——ZJ模型。通过对此概念模型进行模态、扭转刚度和弯曲刚度分析,并与后期的详细有限元模型的特性参数进行对比,验证了ZJ模型建立方法的可行性。ZJ模型的建立和验证过程表明:ZJ模型是一种容易建立、修改灵活且满足车身性能分析要求的有效模型,利用此模型进行车身结构的性能研究可以为后续设计提供重要指导。(3)建立了以ZJ为主体且包含车辆悬架和轮胎的整车耐久性虚拟试验模型,基于虚拟试验场的虚拟耐久性试验环境,在考虑系统中各种结构和材料非线性的情况下,以具有真实道路载荷的综合耐久性虚拟路面为输入,对整车系统进行瞬态响应分析,以获得车身结构较为准确的动态应力应变历程。最后以某新车型的C柱上接头为例,应用应变寿命法进行了T型接头结构的疲劳寿命分析和改进设计,并通过后期的道路试验验证了分析的可行性和有效性。本文研究表明:ZJ模型的构建方法以及基于虚拟试验场的整车耐久性虚拟试验方法,有效解决了车身结构设计初期由于难以建立详细完整的整车有限元模型以及无法进行传统耐久性试验而带来的设计问题,对概念设计阶段的车身结构设计及疲劳耐久性研究起到了一定的推动作用,具有较强的工程实用性。更多还原

【Abstract】 With rapid development and fierce competition in the automobile industry, the demand for the stiffness, strength, durability and safety of the auto-body is higher and higher. This trend requires us to adopt the efficient method to design the structure of the auto-body in the conceptual design phase, which could not only ensure the quality and performance of vehicles, but also shorten the designing cycle and reduce producing costs. In the stage of conceputual design, subjected to the types and the shapes of the vechiles, the layout and the size of the auto-body has little room to change, while the key section and joint structure of the auto-body has more room to do design. Besides, the joints are often the fragile areas of the auto-body. Therefore, it is imperative to do the durability design for the key structrues of the auto-body at the early stage, which will contribute to improving the efficiency of the auto-body design.According to the problems exisiting in the conceputual designing phase, such as the little information about the auto-body structure parameter, the difficulty to build the detailed and complete vehicle finite element model and the impossibilty to conduct the traditional durability test for vehicles, based on the actual structure of the joints, an auto-body conceptual simplified FEA model (ZJ as an abbreviation) is proposed. While the establishment of vehicle durability test model, the simulated analysis for the vehicle durabilty in the virtual road test, and the analysis for fatigue life of the key joints structure, and the optimization in designing were also be accomplished in the research. The main aspects of the studies are as follows:(1) Research status of the conceptual design of auto-body structure, the joint structures and auto-body fatigue durability in the worldwide were introduced. And it put forward the improtance to do the durability design for the key structures of the auto-body.(2) Proposed a simplified FEA model for conceptual auto-body which is based on the actual joints. According to the demands of the layout size of automotive body, the ZJ model was set up by using the basic car’s parameter from the data base of key-sections character, which was composed of actual joints, beam elements and large-size shell elements. The feasibility of the modeling method was validated through analysis of mode, torsion stiffness, bending stiffness of the model, and comparison between characteristic parameters of the later detailed FEA model. The modeling and validation process of ZJ model proves that ZJ is easy-to-build, flexible-to-modify and meet the requirements of the auto-body performance analysis. ZJ model could provide important guidance to subsequent design.(3) We established the vehicle durability virtual testing model, with the ZJ as the dominant position including vehicle suspension and tires. Based on the virtual durability test environment of virtual proving ground, considering structure and material nonlinear characteristic, with comprehensive durability virtual road which has real load as input, the transient response analysis of the vehicle system was carried out to obtain the dynamic stress-strain time history of the auto-body. The C-upper-joint of a new type of vehicle could be taken as an example,the fatigue life analysis and modification design of T-type joint structure are performed by using strain-life method,and the feasibility and validity of the analysis is proved by the road test later .Researches of this paper show that the construction method of ZJ model and the method of vehicle durability virtual test which based on virtual proving ground could effectively solve the problem of establishing detailed vehicle FEA model and the impossibility of conducting the traditional durability test. The study will promote the auto-body structure design and durability research in the conceptual designing process, and has stronger engineering practicability.更多还原