基于多材料匹配的车身关键吸能结构轻量化设计研究

发布时间：2018-10-20 12:31

【摘要】：随着新型轻量化材料的在汽车上的广泛应用,尤其是高强度钢和铝合金以其优良的吸能特性和轻量化效果被大量应用于车身关键吸能结构,因此不同屈服强度轻量化材料之间的匹配问题一直是研究的热点。车身关键吸能结构是保证汽车被动安全性能的重要部件,在车身开发的不同阶段对其进行轻量化设计的同时还要保证它的结构耐撞性能。在概念设计阶段,设计周期较短,需要兼顾成本和轻量化效果并快速确定用材方案。多级吸能薄壁梁一般由多段薄壁梁通过焊接或螺栓连接组合而成,是汽车前后端碰撞压溃区最主要的吸能部件。通过大量昂贵的物理试验或耗时的仿真优化来确定它的用材方案并不理想,而经验公式法则可以在满足一定精度条件下帮助设计者快速而科学的确定用材方案。在详细设计阶段,车身结构和用材方案基本已经确定,此时仍可以通过优化算法在保证车身性能的前提下使各零部件之间的厚度匹配更加合理,实现进一步的轻量化设计。因此,为了缩短该阶段设计周期,选择一种高搜索效率和高精度的优化算法成为工程上亟需解决的问题。概念设计阶段,针对多级吸能薄壁梁替换成轻量化材料后如何选择最合理的厚度既保证它的结构耐撞性能又实现最佳的轻量化效果的问题,提出一种基于经验公式的多材料匹配方法。将该方法应用于方形吸能盒和单帽型前大梁组合的实例后表明,各材料组合换材前后的平均碰撞力误差基本控制在10%以内,且铝合金和双相钢的材料组合轻量化效果最佳,减重达34.4%。此外,除了需要关注轻量化效果还需要考虑成本因素。因此,引入价值函数来评估不同材料匹配方案的综合性能,以帮助汽车企业根据自身发展需求选择最佳的材料匹配方案。最后运用之前的实例分析了交换常数对选材方案的影响。研究结果表明,交换常数的取值与汽车厂商更加看重的是轻量化效果还是成本有关,并决定了最终的最佳材料匹配方案。详细设计阶段,针对复杂耗时的黑匣子优化问题,在混合元模型算法(Hybrid and Adaptive Meta-modeling Method,HAM)的基础上,提出了一种搜索效率和精度更高的多组混合元模型的优化方法(Multiple Hybrid Meta-modeling Method,MHM)。最后将该方法应用于某前舱子系统的关键吸能部件进行厚度匹配优化。结果表明,相比初始设计质量减少5.4kg,下降比例达7.2%,而关键吸能部件的吸能特性并没有下降以及整个子系统的加速度峰值没有增加。本文以车身开发流程为主线,针对不同的开发阶段分别采用不同的多材料匹配方法对车身关键吸能结构进行轻量化设计。通过本文的研究为车身轻量化设计提供了一种新的思路,具有较好的工程应用价值。
[Abstract]:With the wide application of new lightweight materials in automobile, especially high strength steel and aluminum alloy are widely used in the key energy absorption structure of automobile body due to their excellent energy absorption characteristics and light weight effect. Therefore, the matching problem between lightweight materials with different yield strength is always a hot topic. The key energy absorption structure is an important part to ensure the passive safety performance of the vehicle. The lightweight design of the body structure is carried out at different stages of the development of the vehicle body, and the crashworthiness of the structure must be guaranteed at the same time. In the conceptual design stage, the design cycle is relatively short, the cost and lightweight effect should be taken into account, and the material scheme should be determined quickly. Multi-stage energy-absorbing thin-walled beam is usually composed of multi-segment thin-walled beam by welding or bolting, which is the most important energy absorption component in the front and back end of automobile impact crushing zone. A large number of expensive physical experiments or time-consuming simulation optimization are not ideal to determine the material scheme, but the empirical formula rule can help the designer to determine the material scheme quickly and scientifically under certain precision conditions. In the detailed design stage, the body structure and the material scheme have been basically determined, at this time, we can make the thickness matching between the parts more reasonable and achieve further lightweight design under the premise of ensuring the performance of the body through the optimization algorithm. Therefore, in order to shorten the design period of this stage, choosing an optimization algorithm with high search efficiency and high precision has become an urgent problem to be solved in engineering. In the conceptual design stage, the problem of how to choose the most reasonable thickness after replacing the multistage energy-absorbing thin-walled beam with lightweight material not only ensures the crashworthiness of the structure but also achieves the best lightweight effect. A multi-material matching method based on empirical formula is proposed. The application of this method to the combination of square energy absorption box and single cap front beam shows that the average collision force error before and after material exchange is basically controlled within 10%, and the material combination of aluminum alloy and duplex steel has the best lightweight effect. The weight loss is 34. 4%. In addition, in addition to the need to focus on lightweight effects also need to consider cost factors. Therefore, the value function is introduced to evaluate the comprehensive performance of different material matching schemes, in order to help automobile enterprises to choose the best material matching scheme according to their own development needs. Finally, the influence of exchange constant on the material selection scheme is analyzed by using the previous examples. The results show that the value of the exchange constant is related to whether the automaker pays more attention to the light weight effect or the cost, and determines the best material matching scheme. In the detailed design phase, aiming at the complex and time-consuming black box optimization problem, based on the hybrid meta-model algorithm (Hybrid and Adaptive Meta-modeling Method,HAM), an optimization method of multi-group hybrid element model with higher searching efficiency and precision is proposed, (Multiple Hybrid Meta-modeling Method,MHM). Finally, the method is applied to the thickness matching optimization of the key energy absorption components of a front cabin subsystem. The results show that compared with the original design mass, the mass decreases by 5.4 kg, and the ratio of decrease reaches 7.2%, while the energy absorption characteristics of the key energy absorption components do not decrease and the acceleration peak of the whole subsystem does not increase. In this paper, the main body development process is taken as the main line, and different multi-material matching methods are adopted to design the key energy absorption structure in different stages of development. Through the research of this paper, a new way of thinking is provided for the lightweight design of automobile body, which has good engineering application value.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U463.82

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