摘要
节约资源和减少环境污染是世界汽车工业界亟待解决的两大问题,汽车轻量化是实现节能和环保的有效途径。车身重量约占整车重量的40%左右,因此车身轻量化对于整车的轻量化起着举足轻重的作用。车身轻量化设计是多参数、多约束的复杂系统优化问题,首先需要满足耐撞安全性。借助传统有限元分析和“试错法”等手段进行优化设计容易造成计算量过大、优化收敛缓慢甚至无法得到全局最优解等缺点,应用近似模型代替有限元仿真来预测或拟合结构性能响应是国内外研究的前沿和热点。近似模型是一种能够反映设计变量与性能响应之间函数关系的数学模型,通常是结合试验设计和近似拟合方法建立的。目前,根据不同领域的工程应用,对试验设计和近似拟合方法的选择上具有一定的随意性和不确定性,因此车身结构轻量化设计需要对相应的建模方法进行合理评价和选择。本文针对现有车身结构形式,利用近似模型理论结合数值优化算法,对车身结构轻量化设计进行了较为系统的研究,在确保刚度及耐撞性能的前提下,实现车身结构的轻量化。主要研究工作及结论如下:
1)针对车身结构耐撞性能响应具有强非线性的特点,根据近似模型的精度检验指标——均方根误差和最大绝对误差,对比分析均匀设计、拉丁超立方设计及汉默斯里序列抽样这三种常用的现代试验设计方法的抽样方式对支持向量回归近似拟合方法建模的影响。通过对比研究,在满足轻量化设计的“小样本规模”范围条件下,将均匀设计和支持向量回归方法相结合,最适合建立车身结构耐撞性能指标的近似模型。
2)在经典优化理论的基础上,提出了基于近似模型的车身结构轻量化设计流程:结合均匀设计和支持向量回归方法能够建立具有良好整体预测精度的近似模型;基于自适应过程的优化设计通过提升近似模型在最优解处的预测精度,确保得到真实的全局最优解;针对轻量化最优解进行合理的工程修正及仿真验证,能够确保设计方案的工程可行性。根据该设计流程,以车身关键部件——车门为例进行轻量化设计,在确保车门结构刚度及耐撞性能的前提下,实现6.72%的轻量化效果,验证了轻量化设计流程的可行性。
3)针对整车车身结构复杂系统具有性能类型多样且各性能响应非线性程度不一的特点,以某型轿车为例,综合考虑弯曲刚度及侧碰耐撞性能,利用均匀设计和支持向量回归方法建立结构性能指标的近似模型,通过遗传算法优化车身零件的厚度及相应的材料参数,实现车身结构轻量化设计,减少的质量为9.1kg,实现了5.44%的轻量化效果。
Energy saving and environmental protection are two main problems for the world automobile industry and vehicle lightweight is an effective way to realize these two problems. Weight reduction of body structure plays a rather important role in lightweight of full vehicle, for body structure weights about 40 percent of full vehicle. Autobody lightweight design is an optimization procedure with multiple parameters and constraints which should firstly satisfy crashworthiness performance. Traditional design via finite element analysis and“trial and error”method has the disadvantages of huge computational cost and slow convergence, then the optimization design in which approximation model is employed in lieu of finite element simulation becomes a crucial and hot research topic. The approximation model which is built by experimental design and approximation method can express the relationship between design variables and responses. Nowadays the selection of these methods which are used to build approximation model is to some extent arbitrary and uncertain, so this problem should be considered properly for the autobody lightweight design. This dissertation presents a systemic study on autobody lightweight design based on theories of approximation model and optimization method. The purpose of the lightweight design is to achieve weight reduction of the original body structure meanwhile meeting both stiffness and crashworthiness requirements. The studying work is summarized as follows:
1) In the view of high nonlinear characteristics of crashworthiness responses, the comparison of three types of experimental design methods in terms of their capability to generate accurate approximation models for crashworthiness indicators is conducted based on Support Vector Regression method. The result reveals that uniform design integrated with Support Vector Regression method can provide the most accurate approximation model while the number of sample points is limited into the“small scale range”which is suitable for autobody lightweight design.
2) A feasible flow for autobody lightweight design based on approximation model is proposed. In the design flow, approximation model which is built by uniform design and Support Vector Regression method will ensure its global accuracy. The adaptive optimization procedure will improve the local accuracy of approximation models around the optimal result. The proper engineering modification will ensure the feasibility of lightweight result. According to the design flow, a lightweight design for car door structure is conducted which not only realizes the weight reduction effect of 6.72%, but also proves the feasibility of the design flow.
3) The full vehicle structure is a complex system and it contains various performances which have different levels of nonlinearity. The lightweight design for full vehicle body structure considering both stiffness and crashworthiness is conducted by optimizing the sheet thickness and the corresponding material parameters of body components. As a result, the reduced weight of body structure is 9.1kg which realizes the weight reduction effect of 5.44%.
引文
[1] Merklein M., Geiger M. New materials and production technologies for innovative lightweight constructions. Journal of Materials Processing Technology, 2002, 125-126: 532-536.
[2] Joseph C., Benedy K. Light metals in automotive applications. Light Metal Age, 2000, 10: 34-35.
[3]王利,杨雄飞,陆匠心.汽车轻量化用高强度钢板的发展.钢铁,2006,41(9):1-8.
[4] Porsche Engineering Services, Inc. Ultra light steel auto body final report, 1998.
[5] Porsche Engineering Services, Inc. ULSAC validation program engineering report, 2000.
[6] Thorpe M.D., Adam H. ULSAB-Advanced vehicle concepts–overview and design, SAE Paper, 2002-01-0036.
[7]朱士凤,宋起峰. CA1092车身轻量化的研究.汽车工艺与材料,2002,(8):58-62.
[8]张继魁,王保忠,董伦.从2004汽车材料年会看汽车材料的发展.重型汽车,2004,19(6):22-26.
[9]冯美斌.汽车轻量化技术中新材料的发展及应用.汽车工程,2006,28(3):214-220.
[10] Schretzenmayr H. Technical report: the aluminum body of the Audi A8. International Journal of Vehicle Design, 1999, 21(2-3): 303-312.
[11]钱人一. Audi A2车身铝合金空间框架.世界汽车,2001,(4):8-15.
[12] Labelle P., Baril E., Fischersworring A., et al. Alloy used for a new engine block. SAE Paper, 2004-01-0659.
[13] Vert P., Niu X. P., Aghion E., et al. Comparative evaluation of automotive oil pans fabricated by creep resistant magnesium alloy and aluminum alloy. SAE Paper, 2004-01-0658.
[14]冯美斌.从SAE2004年会看汽车材料发展趋势.汽车材料与工艺,2004,22(6):6-12.
[15] Botkin M. E. Structural optimization of automotive body components based on parametric solid modeling. Engineering with Computers, 2002, 18(2):109-115.
[16] Lanzerath H., Schilling R. Crash simulation of structural foam. SAE Paper, 2003-01-0328.
[17] Danyo M. W., Young C. S., Cornille H. J., et al. A design concept for an aluminum sport utility vehicle frame. SAE Paper, 2003-01-0572.
[18]王宏雁,徐少英.车门的轻量化设计.汽车工程,2004,26(3):349-353.
[19]朱平,张宇,葛龙等.基于耐撞安全性仿真的轿车车身材料轻量化研究.机械工程学报,2005,41(9):207-211.
[20]张宇,朱平,陈关龙等.基于有限元法的轿车发动机罩板轻量化设计.上海交通大学学报,2006,40(1):163-166.
[21]杨雨泽,孙凌玉,尹奇凡.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.重庆工学院学报,2007,21(12):6-11.
[22] Ishihama M., Lizuka S., Tanahashi K., et al. Optimization of super-lightweight space-frame vehicle structure. SAE Paper, 2003-01-1709.
[23]沈浩,陈昌明,姚晓冬等.客车车身轻量化分析.客车技术与研究,2003,25(3):8-10.
[24]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.汽车工程,2007,29(7):545-549.
[25]潘锋,朱平,孟瑾.微型货车车架的拓扑优化设计.机械设计与研究,2008,24(2):87-90.
[26] Marklund P. O., Nilsson L. Optimization of a car body component subjected to side impact. Structural and Multidisciplinary Optimization, 2001, 21(5):383-392.
[27] Y. Zhang, P. Zhu, G. L. Chen. Study on structural lightweight design of automotive front side rail based on response surface method. ASME Journal of Mechanical Design, 2007, 129(5): 553-557.
[28] Kodiyalam S., Yang R.J., Gu L., et al. Multidisciplinary design optimization of a vehicle system in a scalable, high performance computing environment. Structural and Multidisciplinary Optimization, 2004, 26(3-4): 256-263.
[29] Sobieszczanski-Sobieski J., Kodiyalam S., Yang R.Y. Optimization of car body under constraints of noise, vibration and harshness and crash, Structural and Multidisciplinary Optimization, 2001, 22(4): 295-306.
[30]张勇,李光耀,孙光永等.多学科设计优化在整车轻量化设计中的应用研究.中国机械工程,2008,19(7):877-881.
[31] Andersson J., Redhe M. Response surface method and Pareto optimization in crashworthiness design. Proceedings of DETC03, ASME design engineering technical conference and information in engineering conference, Chicago, USA, 2003.
[32]王海亮,林忠钦,金先龙.基于响应面模型的薄壁构件耐撞性优化设计.应用力学学报,2003,20(3):61-66.
[33] Wang H. L., Lin Z. Q. Study on optimal design to improve auto-body structural crashworthiness. Journal of Harbin Institute of Technology, 2005, 12(1): 111-118.
[34] Y. Zhang, P. Zhu, G. L. Chen. Lightweight design of automotive front side rail based on robust optimization. Thin-walled Structure. 2007, 45(7-8): 670-676.
[35]邳薇,崔新涛,王树新.基于Kriging模型的汽车车门抗撞性优化设计.组合机床与自动加工技术,2007,(1):29-31.
[36]邓江华,刘献栋,冯国胜.基于神经网络和遗传算法的车身骨架结构优化设计.农业机械学报,2007,38(6):26-29.
[37]张勇,李光耀,钟志华.基于移动最小二乘响应面方法的整车轻量化设计优化.机械工程学报,2008,44(11):192-196.
[38] Timothy W. Simpson, Dennis K. J. Lin, et al. Sampling strategies for computer experiments: design and analysis. International Journal of Reliability and Application, 2002, 2(3): 209-240.
[39]罗世彬,罗文彩,王振国.基于试验设计和响应面近似的高超声速巡航飞行器多学科设计优化.导弹与航天运载技术,2003,(6):2-9.
[40]郭勤涛,张令弥,费庆国.用于确定性计算仿真的响应面法及其试验设计研究.航空学报,2006,26(1):55-60.
[41]游海龙,贾新章,张小波等.试验设计与仿真相结合构造集成电路元模型的方法研究.电子学报,2006,34(6):1159-1162.
[42] Kamal M. M., Wlof J.A. Modern automotive structural analysis. New York: Van Nostrand Reinhold Co., 1982.
[43] John O. Hallquist. LS-DYNA Theoretical Manual. Livermore Software Technology Corporation, Livermore, May 1998.
[44] Saha N. K., Calso S. M., Prasad P. Simulation of frontal barrier offset impacts and comparison of intrusions and decelerations. SAE Paper, 1995-95-0647.
[45] Kelkar A. D., Schulz M. H., Chaphalkar P., et al. Simulation of a car frontal offset impact into a fixed deformable barrier. SAE Paper, 1996-96-2485.
[46]贾宏波,黄金陵等.车身碰撞仿真技术在红旗轿车车身开发中的应用.汽车工程,1998,20(5):257-261.
[47]朱西产,钟荣华.薄壁直梁件碰撞性能计算机仿真.汽车工程,2000,22(2):85-89.
[48] Nagel G. M., Thambiratnam D. P. A numerical study on the impact response and energy absorption of tapered thin-walled tubes. International Journal of Mechanical Sciences, 2004, 46(2): 201-216.
[49] Galib D. A., Limam A. Experimental and numerical investigation of static and dynamic axial crushing of circular aluminum tubes. Thin-walled Structures, 2004, 42(8): 1103-1137.
[50]雷正保,钟志华.汽车碰撞仿真研究发展趋势.长沙交通学院学报,1999,15(1):18-22.
[51] Pickett A. K. Optimization of the crashworthiness of a passenger car using interactive simulations. SAE Paper, 1993-93-1977.
[52]陈万吉.弹性接触问题有限元分析的一个新方法.机械工程学报,1981,17(4):42-322.
[53] Bowden F. P., Tabor D. The friction and lubrication of solids,陈绍澧等译.北京:机械工业出版社,1982,1-4.
[54]刘文卿.试验设计.北京:清华大学出版社,2005.
[55] Lindman H. R. Analysis of variance in experimental design. New York: Springer-Verlag, 1991.
[56] Wang G. G., Shan S.Q. Review of metamodeling techniques in support of engineering design optimization. ASME J. Mech. Des. 2007, 129(4): 370-380.
[57] Redhe M., Giger M., Nilsson L. An investigation of structural optimization in crashworthiness design using a stochastic approach. Structural and Multidisciplinary Optimization, 2004, 27(6): 446-459.
[58] P Zhu, Y Zhang, G. L Chen. Metamodel-based lightweight design of an automotive frontbody structure using robust optimization. Proc. IMechE, Part D: J. Automobile Engineering, 2009, 223: 1-14.
[59] Clarke S. M., Griebsch J. H., Simpson T. W. Analysis of Support Vector Regression for approximation of complex engineering analyses. ASME J. Mech. Des. 2005, 127(4): 1077-1087.
[60]邓乃扬,田英杰.数据挖掘中的新方法——支持向量机.北京:科学出版社,2004.
[61]方开泰.均匀试验设计的理论、方法和应用——历史回顾.数理统计与管理,2005,23(3):69-80.
[62] Anthony A. G., Steven F. W., Michael S. E. Overview of modern design of experiments methods for computational simulation. The 41st Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 2003.
[63] Jin R., Chen W., Simpson T. W. Comparative studies of metamodeling techniques under multiple modeling criteria. Structural and Multidisciplinary Optimization, 2001, 23(1): 1-13.
[64] Kim H. S., Wierzbicki T. Effect of the cross-sectional shape on crash behavior of a 3-D space frame. Impact and Crashworthiness Laboratory Report No.34. May 2000, MIT.
[65]刘惟信.机械最优化技术.北京:清华大学出版社,1994.
[66]雷英杰,张善文,李续武等. MATLAB遗传算法工具箱及应用.西安:西安电子科技大学出版社,2005.
[67]张觉慧,谭敦松,高卫民等.汽车碰撞的有限元法及车门的抗撞性研究.同济大学学报,1997,25(4):450-454.
[68]游国忠,葛如海,程勇等.轿车车门侧面碰撞有限元模拟.中国公路学报,2006,19(5):119-122.
[69] Shan S. Q., Wang G. G. Reliable design space and complete single-loop reliability-based design optimization. Reliability Engineering and System Safety, 2008, 93(8): 1218-1230.