【作者】 田军；

【导师】 孙光永； 王建华；

【作者基本信息】 湖南大学 ， 车辆工程（专业学位）， 2018， 硕士

【摘要】 随着汽车工业的不断发展,能源、环境问题日益突出,目前轻量化技术是实现节能减排的有效手段之一。汽车轻量化设计是在满足结构耐撞安全性能等前提下尽可能的减轻汽车自重。一方面,拓扑优化作为结构优化设计的一种最重要手段,能够在满足耐撞性要求下实现最大减重或者在质量一定情况下极大提高结构的耐撞性。另一方面,薄壁结构不仅质轻,而且能够通过折叠变形吸收大量的能量,具有良好的吸能特性。为此,本文深入研究拓扑优化的设计方法,结合拓扑优化和薄壁结构两者的优势,利用拓扑优化方法进行典型薄壁结构的耐撞性设计。首先本文考虑非线性优化问题,提出了一种基于单元能量的拓扑优化方法。该算法是基于能量和质量之间的两个假设:(1)总质量一定情况下,吸能多的地方应该分配更多的质量;(2)质量变化足够小时,吸能与质量成线性关系。算法以结构吸能为目标、质量或位移为约束,以单元的能量响应信息进行单元厚度的更新,避开了传统优化方法在解决非线性优化问题时需要梯度求导计算灵敏度的困难。然后将提出的拓扑优化方法与变厚度轧制(Tailor Rolled Blank,简称TRB)技术相结合,考虑制造工艺约束,进行汽车上典型结构件的变厚度设计。在准静态三点弯工况下,通过仿真与实验进行对标,验证模型准确性。在确保有限元模型正确的基础上,采用本文提出的优化方法进行了汽车B柱的耐撞性优化设计。为了进一步说明该方法的可行性,选择汽车保险杠进行耐撞性设计。结果表明,相同质量的情况下,优化后汽车B柱和汽车保险杠的吸能性能均得到大幅提升。接下来将提出的拓扑优化方法与多胞结构设计相结合,进行矩形多胞管的截面优化设计。首先在准静态三点弯工况下,对考虑加载历程、不考虑加载历程和施加过滤策略三种方案下的矩形多胞管进行耐撞性优化,优化后结构的吸能分别提高了17.5%、53%和30.4%,且后两种优化得到了明显的拓扑构型。为了进一步研究不同工况对优化结果的影响,针对相同模型,在横向冲击载荷下进行拓扑优化。与准静态工况相比,横向冲击工况下优化后的结构具有不一样的拓扑构型。考虑到汽车的正碰工况,针对轴向动态冲击工况下矩形多胞管进行耐撞性设计。为了进一步验证算法和结果,应用现有的混合自动细胞机(Hybrid Cellular Automata,简称HCA)优化算法在相同载荷和变形位移情况下,进行相同结构的优化设计。两种方法优化后得到了几乎相同的多胞构型。充分说明了该优化方法的正确性和用于多胞结构耐撞性设计的有效性。更多还原

【Abstract】 Vehicle crashworthiness design is one of the most difficult problems being addressed in design optimization.On the one hand,topology optimization method could greatly improve the structural crashworthiness in certain quality.However,traditional topology optimization methods to solve large deformation nonlinear optimization problems encountered great difficulties.On the other hand,Thin-walled structures have been widely used as energy absorbers in automobile and aviation,due to their good performance on energy absorption.However,Traditional design methods of thin-walled structures are not enough to fully release the potential of its energy absorption.Herein,the research presents a topology optimization method to guiding the crashworthiness design of typical thin-walled structures.Considering the nonlinear optimization problem in the crash process,this paper proposes an element-energy-based topology optimization method,which based on two assumptions between elemental quality and energy.The first,there is a linear relationship between the energy absorption and the quality when the quality varies small enough.Secondlly,where more energy is absorbed should be allocated more quality.This method does not need sensitivity analysis by gradient derivation.In order to verify the feasibility of the method,the paper carries out crashworthiness design of TRB structures.The top-hat beam similar to B column in automobile is studied.Firstly,the accuracy of the FE model is validated by experiment data.Then uses the method proposed in this paper to design the automobile B column with TRB structure.In order to further illustrate the practicability of the TRB design method,the optimal design of automobile bum per is carried out.The results show that with the same mass,the energy absorption performance of the optimized B column and automobile bumper is improved greatly.Combining the proposed method with the design of multi-cell structures to optimize the cross section of the rectangular multicell tube.The influence of different strategies on the optimization results are studied.Besides,it carries out crashworthiness design under different working conditions.The results get the obvious topology configuration and the energy absorption performance of the optimized rectangular multicell tube is improved obviously.In the final,the correctness of the method and the feasibility of guiding the crashworthiness design of multi cell structure are illustrated again through comparative analysis the results obtained by the presented method and HCA.更多还原