薄壁双帽型管的轻量化设计及耐撞性研究

发布时间：2018-08-17 19:22

【摘要】：随着人们生活水平的不断提高,汽车数量大幅增加,随之而来的是交通事故频发。汽车安全越来越受到人们的重视,而提高汽车的被动安全性是提高汽车安全的重要举措也是汽车设计的关键环节。同时,为了节能减排,缓解能源危机,汽车设计过程中应当兼顾汽车轻量化。一些新型的轻量化材料如：镁合金、铝合金、碳纤维等在提高汽车安全性和实现汽车轻量化方面体现出巨大的优势。双帽型薄壁管是汽车车身中常用吸能元件,汽车碰撞过程中,尤其是侧面碰撞时,吸能件经常会发生弯曲变形,因此进行双帽型薄壁管横向耐撞性能研究及轻量化设计具有重要的现实意义。本文首先进行了钢板和镁合金的材料性能试验,分别获得了其应力-应变曲线。然后,设计了单一材料的钢双帽型管的准静态三点弯曲试验,并进行了有限元仿真模拟及对标验证。通过有限元模拟分析了双帽型管的吸能特点,变形模式,研究了厚度对双帽型管结构耐撞性的影响规律,研究发现：在保证结构质量不变的情况下,合理搭配上帽和下帽的厚度能够显著改善双帽型管的吸能能力。为了实现传统的钢双帽型管的轻量化,引入了镁合金双帽型管。为研究其横向耐撞性,对镁合金双帽型管进行了准静态三点弯曲试验,同时进行了有限元仿真模拟及分析。结果显示：镁合金双帽型管的变形模式和钢双帽型管大致相同,但是,镁合金双帽型管在受载时出现了局部断裂,这种变形模式某种程度上限制了其吸能能力。为了研究镁合金双帽型管的轻量化效果,对镁合金双帽型管进行了多目标优化,结果表明：镁合金双帽型管相比传统的钢双帽型管体现出良好的轻量化优势,但是,要达到和钢双帽型管相同的吸能值,所需的结构厚度太厚。由此,为了结合钢双帽型管良好的承载能力以及镁合金双帽型管的轻量化优势,引入了钢-镁混合双帽型管,对两种混合管进行了准静态三点弯曲试验和有限元仿真分析,并以上帽和下帽的厚度为变量,并对混合管进行了多目标优化。结果证明：无论从减重效果还是耐撞吸能方面,钢／镁混合管(上钢下镁管)的综合表现都明显优于镁／钢混合管(上镁下钢管)。相比传统的单一材料的双帽型管,上钢下镁混合管综合了钢和镁合金各自的优势,一方面可以明显提高结构的耐撞吸能能力,另一方面又具有良好的轻量化效果,所以上钢下镁混合管作为一种良好的耐撞性组件,可以在汽车车身上加以应用。
[Abstract]:With the continuous improvement of people's living standards, the number of cars has increased significantly, followed by frequent traffic accidents. People pay more and more attention to automobile safety, and the improvement of passive safety is an important measure to improve vehicle safety, which is also the key link of automobile design. At the same time, in order to save energy and reduce emissions and alleviate the energy crisis, the automobile design process should take into account the automobile lightweight. Some new lightweight materials, such as magnesium alloy, aluminum alloy, carbon fiber and so on, have great advantages in improving automobile safety and realizing automobile lightweight. Double-cap thin-walled tube is a commonly used energy absorption element in automobile body. During the process of automobile collision, especially in side impact, the energy absorber will often be bent and deformed. Therefore, it is of great practical significance to study the lateral crashworthiness and lightweight design of double-cap thin-walled tubes. In this paper, the stress-strain curves of steel plate and magnesium alloy were obtained. Then, the quasi-static three-point bending test of steel double-cap tube with single material is designed, and the finite element simulation and calibration are carried out. The characteristics of energy absorption and deformation mode of double cap tube are analyzed by finite element simulation. The influence of thickness on the crashworthiness of double cap tube structure is studied. The thickness of upper cap and lower cap can improve the energy absorption ability of double cap tube. In order to lighten the traditional steel double cap tube, magnesium alloy double cap tube was introduced. In order to study the transverse crashworthiness of magnesium alloy double cap tube, the quasi-static three-point bending test was carried out, and the finite element simulation and analysis were carried out. The results show that the deformation mode of magnesium alloy double cap tube is approximately the same as that of steel double cap tube, but the strain mode of magnesium alloy double cap tube has a local fracture when it is loaded, which limits its energy absorption ability to some extent. In order to study the lightweight effect of magnesium alloy double cap tube, the multi-objective optimization of magnesium alloy double cap tube is carried out. The results show that the magnesium alloy double cap tube has a good lightweight advantage over the traditional steel double cap tube, but, To achieve the same energy absorption value as the steel double cap tube, the required thickness of the structure is too thick. Therefore, in order to combine the good bearing capacity of steel double cap tube and the lightweight advantage of magnesium alloy double cap tube, the steel-magnesium mixed double cap tube was introduced, and the quasi-static three-point bending test and finite element simulation analysis of the two kinds of hybrid tube were carried out. The thickness of the upper cap and lower cap is the variable, and the multi-objective optimization of the mixing tube is carried out. The results show that the comprehensive performance of steel / magnesium mixed pipe (upper steel and lower magnesium pipe) is obviously better than that of magnesium / steel mixed pipe (upper magnesium steel tube) in terms of weight reduction effect and energy absorption resistance. Compared with the traditional double cap tube with single material, the upper and lower magnesium mixed tube combines the advantages of both steel and magnesium alloy, on the one hand, it can obviously improve the energy absorption ability of the structure, and on the other hand, it has a good light weight effect. Therefore, as a good crashworthiness component, upper steel and lower magnesium mixed pipe can be used in automobile body.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U463.83

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