【作者】 武和全；

【导师】 辛勇；

【作者基本信息】 南昌大学 ， 材料加工工程， 2009， 博士

【摘要】 安全、节能、环保是二十一世纪汽车工程领域具有重大意义的研究热点,而汽车的被动安全性是汽车安全性研究的重要环节。对于非承载式车身结构的车辆来说,车架是汽车碰撞中最主要的吸能元件,50%以上的撞击能量均为车架所吸收,因此研究车架的碰撞特性有着重要意义。本文针对某越野车车架碰撞安全性不足的问题,进行了深入研究和分析。通过几何清理、中面抽取、网格划分、单元质量控制等技术,建立了高质量的车架有限元网格模型;以Johnson-Cook本构方程为基础,通过拉伸试验等手段,得到了车架有限元分析的材料模型;通过设置相应的边界条件,对车架进行了有限元刚度分析和模态分析,验证了该车架刚度的可靠性并得到了车架结构的各阶固有频率和振型特性。从汽车对固定墙壁的正面碰撞特性、汽车与汽车正面碰撞的有效模型、汽车与汽车前部偏置碰撞以及汽车前部对固定壁偏置碰撞等方面研究了汽车碰撞的力学分析方法,研究结果表明几何结构参数对汽车碰撞特性的影响有着重要意义。重点研究了车架上的几种典型薄壁梁结构:S型薄壁梁、薄壁梁诱导槽结构以及变截面梁结构等。通过提取实际车架上使用的S梁特征参数,建立了S梁的碰撞模型,并对多变量的S梁进行了因素显著性分析。将响应面法与遗传算法结合起来对S梁进行抗撞性优化分析,得到了S梁的最优设计参数。在分析各种诱导结构特性的基础上,设计了一种变形诱导槽结构。并以此为基础,通过比较各种不同截面薄壁梁的碰撞特性,提出了一种有效的变截面诱导梁结构。将有限元分析与试验设计、神经网络、遗传算法等结合起来对该变截面梁结构进行了抗撞性优化设计。以优化后的典型薄壁梁结构为基础,对越野车车架进行了碰撞安全性优化设计。优化后的车架结构在碰撞过程中的载荷传递路径更加合理,整车的被动安全性得到显著提高。更多还原

【Abstract】 Safety, energy conservation and environmental protection are the three principal problems for the development of automobile industry in the 21^st century. Frame is the most important energy absorption component for those vehicles with non-bearing type of body structure during frontal or rear collisions. More than 50% of the impact energy is absorbed by the frame. So the research of the frame’s collision characteristics is of great significance.This paper carries on a thorough research of a sport utility vehicle’s crashworthiness. Through cleaning up geometry, extracting midsurface, dividing into grids, controlling quality of the elements, the finite element model of automobile frame is established by using thin shell elements. Through tensile testing, the stress-strain curves of frame’s parts are obtained based on the Johnson-Cook constitutive equation. Bending stiffness, torsional stiffness and free modal of the frame is analyzed, based on the finite element model. The results show that the values of the stiffness and mode’s frequency are sufficient for design. From collision of automobile to fix wall, frontal collision of automobile to automobile, offset frontal collision of automobile to automobile, offset frontal collision of automobile to fix wall, this paper studies the mechanics analysis method of the automobile collisions. The results show that the structure parameters are of great importance for automobile collisions.Then this paper focuses research on the following typical thin-walled rail Structures: S-shaped rail, induced trough structure and the rail structure with variable cross-section. An S-Rail impact model is extracted from a true rail used in vehicle frame. Several parameters are proposed as the model variables. Response surface model is interfaced with genetic algorithms to find the optimal parameter values. The relationships between energy absorption and the proposed variables are revealed. S-shaped rail absorbs much energy after its optimal design. An effective structure of deformation induced groove is proposed by analyzing a variety of deformation-induced structural features. Optimal design is carried on the iduced groove to improve its dynamic crashworthiness characteristics of energy absorption. Based on the induced groove, a thin-walled rail with variable section is proposed by comparing a variety of thin-walled rails with different section features. Then the rail is used in the front of a vehicle’s frame. Optimal design method is presented and utilized to obtain optimum crashworthiness design of the thin-walled rail with variable section. The methodology adopted in this research makes use of Design of Experiments （DOE）, Finite Element Analysis （FEA）, Artificial Neural Networks （ANN） and Genetic Algorithms （GA）. The relationships between energy absorption and the proposed variables are revealed and the optimal results are verified through the finite element analysis of thin-walled rail’s collision.Base on optimal design of the typical thin-walled rails, the crashworthiness of a sport utility vehicle’s frame is improved. The path of the force transmission becomes more reasonable after the frame’s optimization during the impacts. And the passive safety of the vehicle is greatly improved更多还原