【作者】 石琴；

【导师】 陈无畏；

【作者基本信息】 合肥工业大学 ， 车辆工程， 2006， 博士

【摘要】 车身作为车辆的重要组成部分,对整车的安全性、动力性、经济性、舒适性及操控性有着重要的影响,同时汽车的个性化也是通过车身设计表现出来。本文以某大客车为研究对象,综合利用现代设计方法中的相关理论,研究了作为汽车三大总成之一的车身结构的静、动态特性及轮胎的刚度特性。 通过建立坐标系,将截面离散化,用截面上关键点的坐标值来描述截面形状,使数与形结合。用代数方法研究几何问题,推导出实用性强、计算精度高且适合计算机编程计算的任意形状开口及闭口薄壁截面的几何特性参数计算公式,解决了准确地确定任意复杂薄壁截面的形心、弯心及形心主轴位置的问题,并给出了算例。 在UG软件中建立车身骨架的几何模型后,用接口程序生成命令流文件将模型导入到ANSYS环境中,建立了车身骨架有限元模型,用有限元理论分析了静态工况下承载式客车车身骨架的强度特性。探讨了承载式车身骨架不同部位的受力特性,提出了通过对骨架结构进行局部改进来提高整体结构强度的方法及对原结构进行改进设计的方案。 在车身结构有限元静态强度分析的基础上,利用ANSYS软件进行了车身结构的模态分析。研究了由路面不平度引起的车身动应力的仿真计算方法。考虑到轮胎结构及其材料和动力学特性的复杂性,在仿真分析中,为了避免由于轮胎的过度简化带来的误差,将整车划分为簧上和簧下两大系统。把簧上部分作为振动系统进行研究,车桥传到悬架的动载荷作为系统的输入,车身弹性体的动态响应(包括车身上各节点的动应力响应)作为系统的输出,建立了系统的动力学方程,根据弹性力学理论推导了车身动应力的计算公式。 研究了车身及悬架弹性对动力悬置系统隔振性能的影响。将发动机及其悬置系统、弹性车身、悬架作为振动分析系统,利用模态综合理论建立了系统的振动分析模型。用四端参数技术,分析了弹性基础情况下动力悬置系统的隔振特性;探讨了在高、底频区,弹性车身对悬置系统的动态特性的影响及在发动机高频激振下,悬置系统的传递率出现过大的原因。 提出了根据轮胎结构的微观变形量分析轮胎侧偏刚度的思路。在对轮胎提出合理的运动假设前提下,推导了轮胎侧偏刚度与轮胎变形之间的定量关系,建立了在侧向力作用下,轮胎有限元模型中相关节点位移与轮胎侧偏角关系的数学模型。以子午线轮胎(185/60R1482H)为例,利用ANSYS软件对子午线轮胎进行了基于非线性模型的有限元分析。将计算结果和试验结果进行了比较,验证了理论计算结果的可靠性。 以结构及工作条件均较简单的集装箱半挂车车架结构为例,在结构设计的开始阶段引入拓扑优化理论,先对结构进行布局优化,获得较合理的初始结构方案,再通过结构参数优化设计,得到满足结构强度、刚度及设计工艺要求的最优结构。在ANSYS软件平台上利用其程序设计语言(APDL)将ANSYS命令组织起来,编写出参数化的用户程序,实现优化设计的全过程。通过用户界面设计语言(UIDL),创建了主菜单和新的函数文件,生成具有行业分析特点和符合用户需要的集装箱半挂车车架优化设计专用软件模块。 研究了车身结构的静动态强度试验中的相关问题,在定远试验场对样车进行了强化试验,分析了样车在各种强化路面上的应力状况,通过对试验结果及理论计算数据的分析,验证了理论分析结果的正确性。更多还原

【Abstract】 Modern vehicle body plays a very important part in the vehicle’s performance. The individual characters of vehicles can be showed through the bodies. The overall objective of this study is to study dynamic characters of bodies and the stiffness characteristic of Tires and static by the means of modern theories and methods of design.The thin wall sections which shapes are very complicate is divided into finite segments. The coordinate axes are built to describe the shapes by the values of the key points. The formulas which can be used to calculate the geometric parameters of the sections easily and accurately are carried out depending on the theory of integral and analytic geometry. The sections’ center position of figure, twist and flexure are fixed precisely. The moment of inertia can be calculated precisely. The practice indicated that this development can contribute to the shape optimization of the thin sections by changing the positions of the notes. The practice indicated that this development can contribute to the shape optimization of the thin wall sections by changing the positions of the key points.The geometric model of the vehicle body is built in Unigraphics software and then is introduced to ANSYS software. Theoretic strength analysis of the body frame was carried out by using ANSYS software. The effects of all the parts on the stiffness of the bus body are discussed. The mechanical characteristics of the rectangular sections which are widely used in buses are given. The method is given to adjust the stiffness of some parts to make them suitable as a whole. Theoretical and experimental results of both improved and original bus body are discussed and commented on. The corresponding experiment was also conductedThe simulation method is studied to calculate dynamic stress of the vehicle body caused by the uneven road. Taking account of the complex nature of tires, the vehicle is divided into two parts which are upon and under the suspensions to avoiding the errors caused by the simplified tires. The system being studied is the part upon the suspensions. The input of the system is the dynamic load translated from axles to suspensions and the output is the dynamic responses of vehicle body. The Equations of vibration of the system are derived. The formulas are got on the basis of the theory of elastic mechanics.It is developed that the cornering force characteristics of tires may be got by researching the micro-deflection of tires. Based on the three suppositions about the motion of tires, the relationship between the cornering force characteristics and the micro-deflection of tires is built. A detailed finite element model of a radial tire is constructed for the prediction of stiffness characteristics by using ANSYS software. The nonlinear mechanical properties of the elastomer were modeled by the Mooner-Rivilin model. A example of the radial tire (185/60R1482H) is given. The calculated results are compared with the experimental results and it is showed that the model reliability is fairly good.The flexible foundation effects on isolation performance of engine-mount systems are discussed. Depending on the theory of modal analysis of vehicle body, equations of vibration for the engine-mount systems, which include engine-mount systems, flexible chassis and suspensions, are derived. The isolation performance of engine-mount systems mounted on the flexiblefoundations is studied by use of Four-End parameters method. It is shown that the flexibility of the foundations has significant effect on the dynamic responses of engine-mount systems especially near the natural frequencies of the supporting structures.The Frame of the Container Semi-dragging Truck is taken to be as an example because of its simple structure and load. The optimal theory of both topology and parameters is introduced into the design of continuum structures to obtain better designs of structures. The procedure can be briefly described as three stages. The first is to get a primal structure depending on the theory of topology. The second is to build a functional structure which is satisfied with the technological requirements. In the final stage the optimal structure of the frame is got depending on the parametric optimization. The optimal design of the frame of a container semi-dragging truck is carries out by means of ANS YS software. The process of it is described in detail. The problem of determining the original structure of the frame is considered. According to result of the topology optimization of the frame the optimal structure of the frame is got depending on the parametric optimization. The comprehensive application of the optimal and parameters theory in the automobile structure design is realized. The dual exploitation of ANSYS software is done by using the languages of ANSYS (APDL and UIDL).更多还原