多目标优化方法在车身结构轻量化设计中的应用研究
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摘要
轿车排放、油耗和碰撞安全法规日益严格,都要求汽车重量不断减少,汽车轻量化技术已成为业界研究的难点和热点。实现车身结构轻量化的途径,一是车身结构优化设计和创新设计；二是研究和开发轻质与高强度车身材料；三是采用先进的车身制造技术。由于高强度钢板在强度、塑性、抗冲击能力、回收使用及低成本方面具有综合的优势,采用高强度钢板及其先进加工工艺成为了当前车身结构轻量化设计的主要方法。
高强度钢板车身结构设计是一个多学科、多目标优化过程,涉及到冲压成形、碰撞安全、结构强度、模态和刚度、NVH和空气动力性等各个方面的性能要求。论文根据轻量化车身结构设计的实践需要,对以试验设计、代理模型、现代优化算法和质量工程为核心的多目标理论体系进行了阐述。本论文主要的研究工作包括以下三个方面：
1)通过某SUV车型的结构特征、受力特点、碰撞变形的力流和能量流分布规律分析,提出了车身结构高强度钢板分布方案。使该车型的高强度钢板质量比例达到54%,处于国内领先水平。
2)提出了车身结构多目标优化方法的算法流程。在采用高强度钢板后,为了确定该SUV车身前端结构关键零件的厚度参数,首先分别建立白车身有限元模型和40%偏置正面碰撞的简化模型；其次在优化模型中综合考虑白车身扭转刚度、最大碰撞力及平均碰撞作用力、碰撞吸能要求和质量最轻等多个性能指标要求,在构建高精度的响应面近似模型的基础上,然后采用非劣性分层遗传算法(NSGA-Ⅱ)对其进行6σ可靠性优化设计；最后运用蒙特卡罗模拟技术对优化方案的鲁棒性进行评价。优化方案的前纵梁变形模式更加合理,其后门槛的加速度响应也得到了改善。
3)白车身模态和40%ODB偏置碰撞试验与仿真结果的比较表明,建立了的白车身和整车碰撞有限元模型的精度符合工程设计要求。在材料升级及结构改进后,40%ODB偏置碰撞的仿真结果表明各关键点的侵入量都有较大幅度的改善。车身结构的轻量化系数也从5.23降低到4.67,处于国内同型车的领先水平。
The lightweight technology of auto body has been the automobile industry's difficult and hot because the more and more strict regulations require of the car emissions, fuel consumption, crash safety, and so on.Usually there are three ways to get the lightweight automobile body structure, through body structure optimized design and innovative design,the development and application of light weight and high strength body material, and using advanced body manufacturing technology. Due to the comprehensive advantages in the performance of the strength, toughness, impact resistance, recycling and cost, high strength steel and advanced processing technology has become the most important way of lightweight design body structure.
High-strength steel body structure design is a multi-disciplinary and multi-objective optimization process including stamping, impact safety, structural strength, mode and stiffness, NVH and aerodynamic performance requirements and other aspects.According to the needs of lightweight body structure designs, the paper carried on the elaboration to the multi-objective optimization theory, including the experimental design, agent model, modern optimization algorithms, and the quality engineering. In this thesis, the research work include the following three aspects:
1)Through the analysis of the body structural feature, the front and side collision deformation characteristic, and the collision force and energy power flow distribution studied,it proposed the automobile body structure high strength steel plate distribution plan,and enables the high strength steel plate quality proportion up to 54%, the domestic leading level.
2) It also proposed the processes and methods of the multi-objective optimization in the body structure design. To match the automobile body front part structure's material and the geometry size after the application of high strength steels, first the finite element model of the body in white and the 40% offset frontal impact model were established; second, the property indexes such as the torsional stiffness of entire body in white, the maximum impact force and the mean force, the collision energy absorption and the minimum mass were considered in the optimization model at the same time, then used the non-inferiority hierarchical genetic algorithm (NSGA-Ⅱ) to carry out 6σreliability optimization design based on the high-precision response surface approximation model;at last, using Monte Carlo simulation technology to evaluate the robustness performance of the result. The optimization results improved the vehicle's collision safety performance, the deformation mode of the front side parts is more reasonable, and the acceleration response in the rear door sill is also improved.
3)The comparison between experiment and simulation of the Body-In-White and 40% ODB offset-crash show that the finite element model meet the requirement of engineering design.The simulation results of 40% offset crash results also shows that all collision response target had been obviously improved after material upgrades and structure improvements.Light-weight coefficient had decreased from 5.23 to 4.67, which is the domestic leading level.
高强度钢板车身结构设计是一个多学科、多目标优化过程,涉及到冲压成形、碰撞安全、结构强度、模态和刚度、NVH和空气动力性等各个方面的性能要求。论文根据轻量化车身结构设计的实践需要,对以试验设计、代理模型、现代优化算法和质量工程为核心的多目标理论体系进行了阐述。本论文主要的研究工作包括以下三个方面：
1)通过某SUV车型的结构特征、受力特点、碰撞变形的力流和能量流分布规律分析,提出了车身结构高强度钢板分布方案。使该车型的高强度钢板质量比例达到54%,处于国内领先水平。
2)提出了车身结构多目标优化方法的算法流程。在采用高强度钢板后,为了确定该SUV车身前端结构关键零件的厚度参数,首先分别建立白车身有限元模型和40%偏置正面碰撞的简化模型；其次在优化模型中综合考虑白车身扭转刚度、最大碰撞力及平均碰撞作用力、碰撞吸能要求和质量最轻等多个性能指标要求,在构建高精度的响应面近似模型的基础上,然后采用非劣性分层遗传算法(NSGA-Ⅱ)对其进行6σ可靠性优化设计；最后运用蒙特卡罗模拟技术对优化方案的鲁棒性进行评价。优化方案的前纵梁变形模式更加合理,其后门槛的加速度响应也得到了改善。
3)白车身模态和40%ODB偏置碰撞试验与仿真结果的比较表明,建立了的白车身和整车碰撞有限元模型的精度符合工程设计要求。在材料升级及结构改进后,40%ODB偏置碰撞的仿真结果表明各关键点的侵入量都有较大幅度的改善。车身结构的轻量化系数也从5.23降低到4.67,处于国内同型车的领先水平。
The lightweight technology of auto body has been the automobile industry's difficult and hot because the more and more strict regulations require of the car emissions, fuel consumption, crash safety, and so on.Usually there are three ways to get the lightweight automobile body structure, through body structure optimized design and innovative design,the development and application of light weight and high strength body material, and using advanced body manufacturing technology. Due to the comprehensive advantages in the performance of the strength, toughness, impact resistance, recycling and cost, high strength steel and advanced processing technology has become the most important way of lightweight design body structure.
High-strength steel body structure design is a multi-disciplinary and multi-objective optimization process including stamping, impact safety, structural strength, mode and stiffness, NVH and aerodynamic performance requirements and other aspects.According to the needs of lightweight body structure designs, the paper carried on the elaboration to the multi-objective optimization theory, including the experimental design, agent model, modern optimization algorithms, and the quality engineering. In this thesis, the research work include the following three aspects:
1)Through the analysis of the body structural feature, the front and side collision deformation characteristic, and the collision force and energy power flow distribution studied,it proposed the automobile body structure high strength steel plate distribution plan,and enables the high strength steel plate quality proportion up to 54%, the domestic leading level.
2) It also proposed the processes and methods of the multi-objective optimization in the body structure design. To match the automobile body front part structure's material and the geometry size after the application of high strength steels, first the finite element model of the body in white and the 40% offset frontal impact model were established; second, the property indexes such as the torsional stiffness of entire body in white, the maximum impact force and the mean force, the collision energy absorption and the minimum mass were considered in the optimization model at the same time, then used the non-inferiority hierarchical genetic algorithm (NSGA-Ⅱ) to carry out 6σreliability optimization design based on the high-precision response surface approximation model;at last, using Monte Carlo simulation technology to evaluate the robustness performance of the result. The optimization results improved the vehicle's collision safety performance, the deformation mode of the front side parts is more reasonable, and the acceleration response in the rear door sill is also improved.
3)The comparison between experiment and simulation of the Body-In-White and 40% ODB offset-crash show that the finite element model meet the requirement of engineering design.The simulation results of 40% offset crash results also shows that all collision response target had been obviously improved after material upgrades and structure improvements.Light-weight coefficient had decreased from 5.23 to 4.67, which is the domestic leading level.
引文
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[2]Benedy J.C.Light metals in automotive applications[J].Light Metal Age,2000,10 (1):34-35
[3]田浩彬,林建平,刘瑞同,等.汽车车身轻量化及其相关成形技术综述[J].汽车工程,2005,27(3)：382-355
[4]Junbo Jia, Anders Ulfvarson. A parametric study for the structural behavior of a Light-weight deck[J].Engineering Structures,2004,26:963-977
[5]王利,朱晓东,张丕军,等.汽车轻量化与先进的高强度钢板[J].宝钢技术,2003,(5)：53-58
[6]朱平,林忠钦,陈关龙,等.铝合金材料在轿车车身轻量化中的应用研究[J].计算机仿真,2006,21(8)：187-190
[7]DORN W, GOMORY R, GREENBERG H. Automatic design of optimal structures[J].De Mechanique,1964,3(1):25-28
[8]YANG R J, CHEN C J. Stress-based topology optimization[J].Structural and multi-disciplinary optimization,1996, (12):98-105
[9]PEDERSON C B W. Topology optimization design of crushed 2D-frames for desired energy absorption[J].Structural and Multidisciplinary Optimization,2003,25(5): 368-382
[10]YANG R J, CHAHANDE A I. Automotive applications of topology optimization[J]. Structural and Multidisciplinary Optimization,1995,9(3):245-249
[11]李红建,邱少波,林逸,等.汽车车身复杂钣金件的拓扑优化设计[J].汽车工程,2003,25(3),303-307
[12]胥志刚,林忠钦,来新民,等.面向车身结构轻量化设计的水平集拓扑优化[J].上海交通大学学报,2007,41(9),1393-1401
[13]范文杰,范子杰,苏瑞意.汽车车架结构多目标拓扑优化方法研究[J].中国机械工程,2006,19,1505-1508
[14]Yamazaki K, Han J.Maximization of the crushing energy absorption of tubes[J]. Structural Optimization,1998,16(1):37-46
[15]L.T.Kisielewic, S.Goto, Y.Matsuoka, et al.Structural crashworthiness optimization of large vehicles using detailed models[C]. PUCA'98,193-205
[16]Dickson K.R, Afzal M.Airbag restraint system design by mathematical crash simulation and design of experiment [J]. SAE paper 901717,1990
[17]Rajiv P, James C.Integration of vehicle interior models into crash up-front process with optimization[J].SAE paper 951107,1995
[18]J.H.Hong, M.S.Mun, S.H.Song. An optimum design methodology development using a statistical technique for vehicle occupant safety[J].Proc Instn Mech Engrs Part D 2001, 215,795-801
[19]S.-Y.Chen. An approach for impact structure optimization using the robust genetic algorithm[J].Finite Elements in Analysis and Design,2001,7:431-446
[20]Smith A E,David M Tate. Genetic optimization using a penalty function[J] Proceedings of the Fifth International Conference on Genetic Algorithms,1993:499-505
[21]Kennedy J,Eberhart R C.Particle swarm optimization[J].IEEE Int Conf Neural Networks Perth,1995,5:1942-1948
[22]陈仙燕,龙述尧.薄壁管抗撞性能的多目标结构优化[J].数值计算与计算机应用,2008,29(3),161-170
[23]孙光永,李光耀,王建华,等.可靠性优化设计在汽车构件耐撞性中的应用[J].计算机辅助设计与图形学学报,2007,19(10),1308-1314
[24]张维刚,廖兴涛,钟志华.基于逐步回归模型的汽车碰撞安全性多目标优化[J].机械工程学报,2007,4(8),142-147
[25]杨雨泽,孙凌玉,尹奇凡,等.兼顾轻量化与吸能性的汽车前纵梁拼焊板设计与参数优化[J].重庆工学院学报(自然科学),2007,21(12),6-11
[26]朱平,张宇,葛龙.基于正面耐撞性仿真的轿车车身材料轻量化研究[J].机械工程学报,2005(9),207-211
[27]韩旭,朱平,余海东,等.基于刚度和模态性能的轿车车身轻量化研究[J].汽车工程,2007,29(7),545-549
[28]梁新华,朱平,林忠软,等.基于有限元法和边界元法的轻量化车身声学分析[J]. 上海交通大学学报,2006,40(1),178-180
[29]张彦,来新民,朱平,等.基于抗凹性的轿车零件的轻量化设计及耐撞性分析[J].机械设计与研究,2004,20(5)：75-79
[30]孙凌玉,Stephen Bian,姚迎宪.车身薄壁梁结构轻量化设计的理论研究[J].北京航空航天大学学报,2004,30(12)：1163-1167
[31]吴宝贵,黄洪钟,原薇.汽车设计的多学科设计优化方法[J].应用科学学报,2005,23(4)：420-423
[32]Yang R J,Gu Lei.Application of Descriptive Sampling and Meta-modeling Methods for Optimal Design and Robustness of Vehicle Structures[C]//43rd Structures,Structural Dynamics,and Materials conference.United States, AIAA,2002:1-7
[33]Maglaras G, Ponslet E,Haftka R T,et al.Analytical and Experimental Comparison of Probabilistic and Deterministic Optimization[J].AIAA Journal,1996,34(7):1512-1518
[34]Sandgren E,Cameron T M. Robust Design Optimization of Structures through Consideration of Variation[J].Computers and Structures,2002,80 (20-21):1605-1613
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