【作者】 刘中华；

【导师】 程秀生；

【作者基本信息】 吉林大学 ， 车辆工程， 2004， 硕士

【摘要】 目前的国内正碰试验中,关于乘员保护指标规定的法规试验, 仅对乘员伤害指标及汽车前部的吸能性进行总体评价,而不能进一步根据用户要求同时对汽车前部各个构件的改进设计得出有价值的评价，也就是不能提供汽车车身安全设计的前部构件的参数化模型。所以有必要建立车身前部撞压变形特性和吸能特性与乘员伤害评价指标之间的相关性参数模型。这种参数化模型的研究是建立在对车身前部各个吸能部件撞压变形和吸能特性的研究基础上的。在研究的初始阶段，可以先对关键部件进行变形和吸能特性的基础性研究。本论文对轿车正碰中的主要吸能件前纵梁薄壁结构进行了碰撞模拟仿真，从乘员保护的角度出发，就其变形和吸能特性进行了一些参数化的探讨和分析，提出了前纵梁薄壁结构的一些改进措施，获得了相对较好的变形和吸能特性。本论文的主要内容如下：1. 在阅读大量文献的基础上，介绍了实车碰撞试验法规的现状和发展趋势；考察了国内外汽车被动安全性研究现状，概述了汽车被动安全的研究方法、取得的最新成果及最新发展动态。对国内外正面碰撞研究的情况以及国内正面碰撞研究的局限性也进行了介绍。结合乘员保护对前纵梁薄壁结构研究的意义进行了阐述，并介绍了汽车抗撞性模拟仿真的研究情况和一般所用到的仿真软件。2. 介绍了碰撞软件广泛采用的显式非线性有限元理论。概述了显式非线性有限元理论的一些主要的方程和算法。3. 基于乘员保护，根据整车的理想碰撞力响应，推出前纵梁的理想碰撞力-变形曲线，并结合常用的吸能特性评价参数，给出了前纵梁薄壁结构的评价方法。运用碰撞仿真软件对小红旗前纵梁薄壁结构进行了建模，就建模中的应注意的各个细节进行了讨论。例如网格的划分，材料和焊点的定义，时间步长和沙漏参数的控制的等。并对建模方法进行了验证。碰撞试验和<WP=79>仿真模拟的碰撞力-变形曲线的对比结果表明，本文的所采用的建模方法与实际是相符合的。可以用来对一系列材料和建模方法相同的薄壁直梁进行建模。为了得到薄壁直梁设计的参数化经验，本文建立了小红旗的前纵梁薄壁结构模型。结合薄壁梁的变形和吸能评价参数，对一系列影响薄壁直梁变形和吸能特性的参数进行了讨论。讨论了薄壁直梁截面的形状和焊接形式，触发诱导机构位置、大小和形状，薄壁梁的壁厚以及加强板结构等对薄壁直梁变形和吸能特性的影响。最后给出了相对吸能特性较好的薄壁直梁模型。本文的数值仿真方法、研究内容和结果对于前纵梁的设计有一定的技术参考价值，。从建立整车变形和吸能特性与乘员响应之间的相关性参数化模型的角度出发，本文是进行汽车正面碰撞下车身前部变形特性对乘员伤害指标影响研究的一个基础性研究，上述工作将对进一步研究汽车正面碰撞下车身前部变形特性对乘员伤害指标影响，进而实现汽车的轻量化设计、总吸能的提高、碰撞力-波形曲线的改善等有重要意义。更多还原

【Abstract】 The actual legislated regulations about vehicles’ front collisions can only estimate the occupant’s injury index and the energy absorbing characteristic of the vehicles’ front structure as a whole, but can not educe valuable conclusions on improvement design of each component of the frontal structures to satisfy the producer’s requirements. So it is necessary to establish the interrelated parameters’ model between occupant’s response and the characteristic of deformation and energy absorbing of vehicle’s front end. The study of the interrelated parameters’ model of this kind is base on the research on the characteristic of deformation and energy absorbing of each component of the front structures. In the initial stage of this study, we can study the characteristic of deformation and energy absorbing of key component of the front structure. The front side rail is the key energy absorbing component of the vehicles’ front structure. In this paper, the numerical crash simulation on the front side rail is made. Aimed at occupant security, the characteristic of deformation and energy absorbing of the front side rail is also discussed. At last, some measures about improvement on the characteristic of deformation and energy absorbing of the front side rail are obtained.(1) The internal and external status, research and developing methods, up to date achievements and developing trends of the automobile passive safety are introduced. The status and the shortage of the actual legislated regulations for full frontal collision are discussed. The internal and external research on full frontal collision and the shortage of the civil research are introduced. Combined with occupant security, the meaning of research on the front side rail is discussed. The development of crash simulation and the simulation software are also introduced.(2) The theory of the explicit nonlinear finite element which is largely adopted in the crash simulation software is introduced.(3) Based on occupant security, the optimized force-deformation curve of the front side rail is derived from the optimized curve of full vehicle. <WP=81>Combined with some energy absorbing assessment index, the evaluation methods about the characteristic of deformation and energy absorbing of the front side rail are offered.(4) The model of thin-walled beam of the front side rail is set up by the use of the software ESI/PAM-CRASH. The details about modeling the thin-walled beam which include the plot of gridding, the definition of materials and spot weld, the control of time step and hourglass parameter and so on are discussed. The means of modeling are proved to be right by the comparison test curves with the simulation curves. So the means of modeling can be used to model thin-walled beam.(5) In order to obtain the parametric design experience of thin-walled beam, a model of thin-walled beam of the front side rail of HongQi CA7200 is set up. Combined with the energy absorbing assessment index, a series of parametric methods about improving the characteristic of deformation and energy absorbing are discussed, including the cross-section ,the mode of jointing, the trigger structure’s place, size and shape, the thickness of beam, the strengthening panel and so on. At last, a improved model of HongQi CA7200 is offered.The numerical simulation methods, content and result of this paper have some reference values of technology for the design of the front side rail. From the point of setting up the parametric model between occupant security and the characteristic of the deformation and energy absorbing of the full vehicle, this paper is a basic start of studying the connection between occupant security and the characteristic of the deformation and energy absorbing of the full vehicle. The research and analysis of this paper have important meaning in further studying the characteristic of the deformation of full vehicle and its influence on occupant security index.. Also it is important for the vehicle’s lightweight design.更多还原