外文翻译：轿车车身的碰撞有限元模型分析

附录1汽车的碰撞安全性越来越得到人们的重视,不论是对轿车、小客车或其它类型的车辆。

由于进行碰撞试验往往需要许多时间与金钱,计算机仿真就是一条较好的方法。

而且,汽车被动安全性研究的有限元方法的发展,非线性动力显式有限元方法的进步,使得利用计算机仿真来进行汽车安全性评价与改进成为可能。

目前,各大汽车公司与研究机构已着手研究从仿真分析的结果中推演出进一步的修改方案,达到在汽车重量与碰撞特性等方面最优的研究。

本文以提高汽车耐撞性为目标,以某型七座小客车的初步设计方案为基础,建立了用于正面碰撞仿真的前部碰撞有限元模型,并进行了计算机碰撞模拟,提出了改进方案,提高了汽车的被动安全性设计水平,从而提高了新车型满足碰撞全法规的成功率。

在对汽车进行碰撞性能有限元分析时,汽车整车的建模工作量巨大。

本文中的整车有限元模型中的各个零件均由各零件的U G或CATIA 格式的几何模型转入HYPERME2SH 有限元建模软件并进行网格划分,再进行装配而成。

碰撞分析的有限元模型的节点数和单元数都超过了14 万,规模较大。

有限元分析软件采用LS2DYNA ,它是当前在汽车碰撞有限元仿真中应用较多的一个非线性动力显式有限元软件,它的主要算法采用Lagrangian 描述增量法,利用显示中心差分法离散时间域,积分时间步长大小受Courant 稳定性准则制约。

整车结构由100 多个元件装配而成。

建模时,连接的刚度和强度根据实际情况确定。

模型中的板壳单元以Be2lytschko - Tsay 四边形壳单元为主。

而节点也分为常规节点和模拟部分焊点情况的带失效的固连。

发动机和变速器在整车碰撞中的变形不予以考虑,其材料定义为刚性材料。

车门和车体的连接是通过铰链和门锁固定的,在数值仿真中,通过约束对应节点的位移自由度建立球铰模型来模拟。

考虑到研究中仿真的碰撞方式是最为典型的正面碰撞,在正面碰撞过程中,A 柱前部的车身结构是变形吸能的主要器件,其变形的模式极为复杂,而中柱之后在碰撞过程中几乎不发生变形。

为节省计算时间,将车身的前部单元划分较密,中柱之后则较稀。

计算中采用弹性刚度沙漏控制。

按照CMVDR294 碰撞法规的要求,小客车以50km/ h的速度正面撞击刚性墙。

设置的初始边界条件与实车实验的初始条件相同,模拟该车以50km/ h 的初速度正面撞击刚体墙。

在有限元计算后进行后处理,并对模拟计算的结果进行了分析。

模拟结果显示,变形主要集中在车辆前部,车辆后部基本没有变形。

由于前纵梁的问题较大, 为了提高其碰撞性能, 解决方法是改变其局部结构来得到更合理的变形模式和更好的能量吸收特性。

两处产生塑性铰的局部区域,可以增加两块加强板来改善纵梁的总体的吸能情况。

改进设计后的小客车前围部分零件。

每年的道路交通事故数和死亡人数以及由此带来的经济损失是惊人的。

汽车被动安全性的重要性在世界范围内得到认同。

人们认识到碰撞事故是不可避免的。

被动安全的研究从60年代开始不断探入的开展越来越向着多样化、专业化和高科技化的方向进行。

早期的汽车耐撞性研究主要采用实验手段进行。

汽车碰撞实验是破坏性实验, 有着种种局限性。

其实验成本很高, 实验周期长, 而且必须先制造出样车。

1970年以来, 计算机在汽车设计中的成功应用,使汽车工业事实上进入了一个新的发展阶段。

在汽车碰撞领域中首先应用于计算机仿真的模型是〕提出的集中参数模型。

随后显式有限元方法的发展和成熟, 使这一方法被迅速的应用到汽车碰撞过程的仿真中来。

1985年以德国大众汽车公司出品的轿车为原型的第一个有限元模型成功地模拟了轿车的正面碰撞过程图。

有限元汽车碰撞数值仿真的运算代价较低, 设计周期短和可以实现无样车的虚拟碰撞实验等显著的优点使各大汽车制造商在近15年来积极地开展这方面的工作。

碰撞仿真已被运用到贯穿概念可行性研究到整车设计和开发的全过程。

同时由于80年代以来计算机运算速度和存贮能力的飞速提高、显式有限元方法的发展和成熟、对于薄壁钢结构在高速碰撞条件下如损伤、断裂等新的本构关系的认识,以及各种连接方式的数值模型的建立, 使汽车碰撞的计算机仿真成为一门新兴的学科。

汽车碰撞过程是一个涉及大位移、大变形、大转动的复杂非线形的动态接触问题。

为了解决计算效率的问题, 通常采用显式算法。

在碰撞仿真中, 准确的模拟碰撞过程的关键是采用合理的接触算法和能够描述碰撞条件下材料本质的材料模型。

本文以某型轿车为原型, 建立了白车身的碰撞有限元模型, 并针对计算效率和准确性进行了着重分析。

本文进行了对正面固定刚性墙的碰撞性能仿真。

碰撞仿真的变形结果和整车实验结果较为吻合, 车身典型位置的加速度时间曲线和实验曲线的比较显示本文所建立的白车身有限元数值仿模型是真实准确的。

现代轿车的车身普遍采用承载式车身结构, 与早期的非承载式的车身结构不同, 承载式车身没有以前用来承重的贯穿车身全长的车架结构, 而是由冲压成型的0.7-0.8mm的薄钢板通过点焊、搭接而成的, 这样既提高了整车的抗扭刚度又减轻了车重。

承载式车身在发生高速正面碰撞时, 整个前部车身发生溃缩, 碰撞能量主要通过车身结构的变形来吸收。

因此对于碰撞仿真来说, 就必须建立一个能描述碰撞接触区域内车身结构及其连接关系的精确的几何模型。

获取这样的几何模型的最方便的途径是内部CAD数据, 但是由于CAD和CAE本质的不同使得描述了很多加工和装配上工艺细节CAD的数据在CAE建模中反而成为工作的障碍。

本文建立的轿车白车身几何模型采用了曲面反演技术, 即利用高精度三座标测量仪CMM对覆盖件的主模型或封装模型进行曲面扫描, 对得到的离散数据一般称为云团数据进行拟合和光顺处理,从而得到车身的三维模型。

获取了白车身的几何模型之后进行单元离散化就得到了碰撞有限元模型。

汽车碰撞仿真中需对计算效率问题加以特别的关注。

因为象整车碰撞仿真这样的大规模数值计算动辄进行上百小时, 占用了大量的机时, 进行重复计算是很困难的。

汽车碰撞是一个动态的大位移和大变形过程,系统具有几何、材料和边界等多重非线性特征。

因此,汽车碰撞的数值计算分析一般采用非线性动态显示有限元分析。

有资料显示,汽车发生碰撞事故时,发生正面碰撞(包括斜碰)的概率在40%以上,居于各种碰撞类型之首。

因此,研究正面碰撞特性,对降低乘员的伤害非常重要。

本文采用ANSA和LS - DYNA对国产某轿车的保险杠横梁正面撞击刚性墙过程进行了数值仿真,并对保险杠横梁的结构进行优化设计,说明结构优化后的横梁碰撞安全性优于原始结构。

大变形碰撞问题通常需要耗费大量的计算时间,如何提高求解速度是求解的主要问题。

与常规有限元计算不同的是,为了避免大型联立方程组求解,提高计算速度,碰撞分析软件一般采用显示算法。

附录2The safety car collision has been more and more people's attention, whether for cars, small buses or other types of vehicles. As a result of a collision test often requires a lot of time and money, computer simulation is a better way. Moreover, the passive vehicle safety study of the development of the finite element method, nonlinear dynamic explicit finite element method of progress, making use of computer simulation for vehicle safety evaluation and improvement is possible. At present, the major car companies and research institutions has embarked on research from the analysis of the simulation results show a further push to amend the proposal to reached in a collision with the vehicle weight, and other characteristics of the best aspects of the study. In this paper, in order to improve the crashworthiness car as the goal, to a seven-passenger preliminary design for the foundation, set up positive for the simulation of the collision before the collision the Department of finite element model, and a computer simulation of the collision, a program to improve To improve the car's passive safety design standards so as to enhance the all-new models to meet the collision regulations of the success rate.In the car collision on the performance of the finite element analysis, the vehicle's enormous workload modeling. In this paper, the finite element model of vehicle in all the parts are parts of the CATIA or UG format of the geometric model into HYPERME2SH finite element modeling software and mesh, and then carried out by the assembly. Collision Analysis of the finite element model of nodes and units are more than 140,000, and larger. Finite element analysis software used LS2DYNA, it is in the car crash in the application of finite element simulation of a more dynamic non-linear explicit finite element software, its main method used to describe Lagrangian incremental method, showed that the use of discrete-time center-difference Domain, the time stepsize of the points by the Courant stability criteria constraints.Structure of the vehicle by more than 100 components from the assembly. Modeling, to connect the stiffness and strength to determine the actual situation. The shell model unit to Be2lytschko - Tsay quadrilateral shell element-based. The nodes are divided into conventional analog nodes and part of the solder joints of the solid even with failure. Engine and transmission in vehicle collision in the deformation not be taken into account, the material is defined as rigid materials. The doors and body are connected through the hinges and locks fixed, in numerical simulation, bound by the corresponding node through the displacement of the establishment of degrees of freedom model to simulate the ball joints.Taking into account the study of the collision simulation is the most typical collision positive, positive in the course of the collision, A column of the front body structure is a deformation of the main energy absorption device, the deformation of complex patterns, and in column after a collision in the process of Almost no distortion. In order to save calculation time, the body of the front unit more closely, in the column after more rare. Elastic stiffness in the calculation used to control the hourglass.CMVDR294 collision regulations in accordance with the requirements of small passenger cars to 50km / h speed frontal impact in the rigid wall. The initial set of boundary conditions and the experimental car is the same as the initial conditions, the simulation of the car to 50km / h speed frontal impact in the beginning of the rigid wall. In the finite element method after the post-processing, and the simulation results are analyzed. The results show that the deformation concentrated in the front of the vehicle, no deformation at the rear of the vehicle.As the beam before the larger issues, in order to improve the performance of its collision, the solution is to change its regional structure to a more rational pattern of distortion and better energy absorption characteristics. Produced two plastic hinge of the local area, will increase two to strengthen the board to improve the overall beam of energy absorption situation. To improve the design of passenger carsbefore some of the parts Wai.The annual number of road traffic accidents and death toll, as well as the resulting economic losses are staggering. Automotive passive safety of the importance of the world it was accepted. It is recognized that collisions are inevitable. Passive safety research from the age of 60 began to explore the means to carry out more and more toward diversification, professional and high-tech direction.Early automobile crashworthiness research using experimental means. Automobile collision experiment is destructive experiment with various limitations. The high cost of the experiment, the experimental long, but must first create kind of car. Since 1970, computers in the design of the success of the automotive applications, so that in fact the auto industry has entered a new stage of development. In the first car collision in the field of applied computer simulation of the model proposed by the focus is〕 parameter model. Followed by explicit finite element method and the development of mature, so that this method has been applied to the fast-car collision simulation in the course of the past. In 1985 by Germany's Volkswagen production cars for the first prototype of the finite element model successfully simulated the car's front collision course map.Finite element simulation of vehicle collisions lower the cost of computing, and short design cycle can be achieved without the kind of virtual car collision experiments, such as significant advantages so that all the major car manufacturers in the past 15 years to carry out active work in this area. Collision simulation has been applied to study the feasibility of the concept through the vehicle design and development of the whole process. At the same time, since the age of 80 due to the computing speed and storage capacity of the rapid increase in explicit finite element methods for the development and maturity, the thin-walled steel in conditions such as high-speed collision damage or crack the new constitutive relation of understanding, As well as a variety of ways to connect the numerical model, so that the vehicle collision computer simulation has become an emerging disciplines. Automobile collision involving a large displacement, large deformation and large rotation of the complex non-linear dynamics ofthe contact problem. In order to solve the problem of computing efficiency, usually explicit algorithm. In the simulation of collision, the accurate simulation of collision course, the key is to adopt a reasonable method of contact and be able to describe the collision of the nature of the material conditions of model material.Based on a prototype for the car, a white body finite element model of the collision, and for calculating the efficiency and accuracy of the analysis focused. This article was positive for the fixed rigid walls of the collision simulation performance. The simulation results of the collision and deformation of the vehicle is more in line results, the typical location of the body's curves and acceleration of time compared with the experimental curve in this paper shows that the establishment of the body in white like finite element model is true and accurate.Modern cars commonly used by body-bearing body structure, with the early non-bearing structure of the body, carrying the body-weight people do not have to run through the length of the body frame structure, but by stamping forming the 0.7-0.8mm The thin plate through the spot, by lap, so that not only improved the vehicle's torsional rigidity and reduced weight. Body-bearer in the event of a positive high-speed collision, the front of the entire body shrink collapse occurred, the collision energy, primarily by the deformation of the structure of the body to absorb. For the simulation of collision, it is necessary to establish a description of the collision to contact the region connection body structure and the relationship between the geometric precision of the model. Access to such a geometric model of the most convenient way to internal CAD data, but because of the nature of CAD and CAE's description of the different makes a lot of processing and assembly processes on the details of the CAD data in the CAE modeling instead become an obstacle to the work.In this paper, the car body in white geometric model of the surface using inversion, that is, the use of high-precision coordinate measuring instrument panel on the CMM model for the main package or model surface scan, to be known as the discrete data cloud data Fit smoothness and to carry out processing, in order to get three-dimensional modelof the body. Access to a white car after the geometric model of discrete units have been on a collision finite element model.Automobile collision simulation to be calculated on the efficiency of special concern. As the vehicle collision because such a large-scale numerical simulation calculation at every turn for more than 100 hours, taking up a large number of machines, double it is very difficult.Automobile collision is a dynamic large displacement and deformation of the process, the system has a geometric, material and multiple non-linear features of the border. As a result, car collision numerical analysis of general nonlinear dynamic finite element analysis shows. Are indications that the vehicle collision accident, the collision occurred in front (including oblique impact) in the probability of more than 40% in various types of collisions in the first. As a result, a positive study on characteristics of the collision, the crew lowered the damage is very important. In this paper, ANSA and LS - DYNA on the bumper of the car made a positive impact beams rigid wall process simulation, and bumper beams designed to optimize the structure shows that the optimized structure of the beam collided security is better than the original structure.Large deformation problem of collisions usually takes a lot of time calculating how to improve the speed of solving the main problems to solve. With the conventional finite element difference is that in order to avoid large-scale simultaneous equations to solve, raising the speed of calculation, analysis of the collision use of software in general show that algorithm.。