摘 要

近年来，国内汽车行业发展迅速，普通家庭的汽车保有量也持续增加，随之而来的是日益凸显的交通事故问题。目前，各类交通安全事故主要分为四类，而不论国内外，占据事故比例最大的均为正面碰撞。因而，汽车在发生正面碰撞时的被动安全性能显得尤为重要。以此为背景，本文提出了分析汽车在正碰条件下车身吸能系统的耐撞性这一课题。

本文借助计算有限元分析软件Hypermesh和LS-Dyna，根据指定参数的汽车车身前端吸能系统进行有限元分析。通过对比市面上已有的汽车前部吸能系统所采用的材料，结合众多研究者选取的材料，本文选取AA5357、DP590和780TR三种材料作为变量，对车身吸能系统的前防撞梁、吸能盒和前纵梁进行材料的赋予，以此组合成不同的吸能系统。具体研究内容如下：

1. 选取吸能量、比吸能和系统整体溃缩量作为评价指标，分别对单一材料吸能系统、两种材料组合的吸能系统和三种材料组合的吸能系统三大类进行计算结果的分析。在每个大类中根据评价指标比较出性能较为优越的组合。再以单一材料吸能系统作为对照组，在筛选出的组合中进行二次对比分析，最后选取两个耐撞性最优的组合，进行下一步分析。

2.将碰撞条件设置为5°与15°的斜角碰撞，对已选择出的两种组合材料吸能系统进行进一步的仿真分析。比较两者的分析结果，综合正面碰撞和斜角碰撞的数据，选取其中耐撞性最好的一组吸能系统，并记录此时三个吸能部件所采用的材料。

3.以各个吸能部件所采用的材料为单一变量，基于已有的有限元仿真分析数据，对比各种材料组合情况下，正在文中给定的三种材料中，各部件最适合采用材料，并排列三种材料应用于各部件的优先级顺序。

研究结果表明：

1.在本文采用的三种材料中，耐撞性最优的组合是前防撞梁采用AA5357铝合金，吸能盒采用DP590高强钢，前纵梁采用780TR高强钢。

2.三个部件中，前纵梁的材料整体强度应该最大，三种材料的优先级顺序为780TR＞DP590＞AA5357；前防撞梁应该有适当的刚度，材料的优先级顺序为AA5357gt;DP590且AA5357gt;780TR；吸能盒应该选用屈服强度较低的材料，其采用材料的优先级顺序为DP590＞AA5357且DP590＞780TR。

本文的特色：提出用不同材料的部件组合的车身吸能系统，利用有限元仿真方法研究其耐撞性，并分析其中耐撞性最好的组合。

关键词：耐撞性；多材料；吸能系统；碰撞安全

Abstract

In recent years, the domestic automobile industry has developed rapidly, and the number of car ownership for ordinary families has also continued to increase, bringing with it the increasingly prominent problem of traffic accidents. At present, all types of traffic safety accidents fall into four categories. Regardless of whether they are at home or abroad, the largest proportion of accidents that have been occupied are frontal collisions. Therefore, the passive safety performance of the car in the event of a frontal collision is particularly important. Based on this background, this paper puts forward the problem of analyzing the crashworthiness of front end structure of auto-body under the condition of frontal collision.

In this paper, FEA analysis software Hypermesh and LS-Dyna are used to perform finite element analysis based on the specified parameters of the front end structure of auto- body. By comparing the materials used in the existing front vehicle energy-absorbing system on the market and combining the materials selected by many researchers, this paper selected three materials, AA5357, DP590, and 780TR, as the variables, the bumper, the crash box and the front rail are given material to be combined into different front end structure. The specific research content is as follows:

1. Selecting energy absorption（E）, specific energy absorption（SEA）, and overall system collapse as evaluation indices, the results of the three categories of single material energy absorption system, energy absorption system with two materials, and energy absorption system with three materials are analyzed. In each major category, a combination of superior performance is compared based on the evaluation indicators. Then, a single material energy absorption system was used as a control group, and a secondary comparative analysis was performed in the selected combinations. Finally, two combinations with the best crashworthiness were selected for the next analysis.

2. The collision conditions were set to 5° and 15° oblique angles, and the two selected composite energy absorption systems were further simulated and analyzed. Comparing the analysis results of the two, combining the data of frontal and oblique collisions, select a group of energy absorbing systems with the best crashworthiness, and record the materials used for the three energy absorbing components at this time.

3. The materials used for each energy-absorbing component are single variables. Based on the existing finite element simulation analysis data, compared with various material combinations, among the three materials given in the text, each component is most suitable for the use of materials and arranged. Three materials are applied to the priority order of each component.

Research indicates:

1. Among the three materials used in this paper, the combination with the best crashworthiness is AA5357 aluminum alloy for the bumper, DP590 high strength steel for the crash box and 780TR high strength steel for the front rail.

2. In the three components, the overall strength of the material of the front rail should be the largest, the prioritization order of the three materials is 780TRgt;DP590gt;AA5357; the bumper should have appropriate stiffness, and the priority order of the materials is AA5357gt;DP590 and AA5357 gt; 780TR; crash boxes should be made of a material with a low yield strength, the order of priority of the materials used is DP590gt;AA5357 and DP590gt;780TR.

The characteristics of this article: It proposes a front end structure of auto-body that uses a combination of different material components, uses a finite element simulation method to study its crashworthiness, and analyzes the best combination of crashworthiness.

Key Words:Crashworthiness;multiple materials;front end structure；collision safety

目 录

摘 要 I

Abstract II

第1章 绪论 1

1.1研究背景、目的及意义 1

1.2国内外研究现状 2

1.3国内碰撞安全法规 3

1.3.1碰撞标准与伤害指标 3

1.3.2耐撞性结构的设计要求 3

1.4相关软件概述 4

1.4.1 HyperWorks 4

1.4.2 LS-Dyna 5

1.5本文主要研究内容 5

1.6 本章小结 6

第2章 有限元分析方法与评价指标 7

2.1 有限元分析方法 7

2.1.1有限元法与有限差分法 7

2.1.2显式积分算法 7

2.2耐撞性评价指标 8

2.2.1 吸能量E 8

2.2.2 比吸能E_SEA 8

2.2.3 平均碰撞力 8

2.2.4 碰撞力峰值 9

2.2.5 碰撞力效率F_CFE 9

2.3 本章小结 9

第3章 车身前部吸能系统有限元建模 10

3.1车身前部吸能系统结构概述 10

3.1.1 前防撞梁与吸能盒 10

3.1.2 前纵梁 10