工艺切口与坯料网格剖分算法的研究
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摘要
工艺分析与设计是汽车覆盖件产品开发的核心环节之一,它直接关系到产品的质量,生产成本,生产效率和模具的寿命。随着汽车工业的高速发展,对覆盖件的工艺设计提出了越来越高的要求,传统的工艺设计已经无法满足当今时代的要求。近年来,随着计算机软硬件技术、计算机图形学技术、人工智能技术和有限元理论的发展,板料成形的数值模拟技术已逐渐成为工艺分析及优化设计的有效工具。
本课题来源于国家自然科学基金项目:面向自主设计的汽车覆盖件成形性快速仿真及工艺优化技术研究,项目批准号为50575080。在华中科技大学模具国家重点实验室开发的基于动力显式算法的FASTAMP软件的平台上,运用计算机图形学技术和有限元理论,提出并实现了基于网格自适应加密与减密的工艺切口算法,实现了初始板料网格剖分算法。
本文深入地研究了求解板料成形问题的动力显示算法中的一些关键技术,包括板料成形动力分析的BT(Belytschko-Tsay)壳单元数学模型和由单点积分引起的零能模式的解决方案;重点介绍了网格自适应加密与减密技术,包括该技术的判断依据,单元的加密算法,单元的减密算法和加密或减密后单元的物理场量的继承关系;较为简单地介绍了动力分析显式求解方法以及该算法的稳定条件。
本文通过对多种工艺切口算法进行研究比较,分析了它们的优缺点,提出了一种新的面向网格自适应加密与减密的工艺切口算法,建立了加密网格剖分模板库。算法采用向前推进方式对切边线经过的单元进行网格调整,通过网格映射方法完成新旧单元体系下物理量信息传递。将算法集成到基于动力显式算法的FASTAMP软件中,选取实际生产的汽车覆盖件进行成形模拟,优化了工艺切口时的模具行程,以及与切口相关的参数,例如切口的大小、位置和形状。将工艺切口方案应用于实际拉深成形中,其成形结果不仅验证了数值模拟结果的准确性,同时也说明工艺切口算法的实用性。
本文根据工艺切口模拟算法中网格调整的思想提出了一种新的平面网格剖分算法。建立了板料轮廓的最小包容区域,以该区域进行适当的放大,在放大的区域内进行四边形单元网格的划分,根据板料轮廓线对放大区域的网格进行调整,删除板料轮廓线外围单元及其上的节点,并对轮廓线内围单元的单元号和节点号进行重新编号。最后通过许多实际用例验证了本算法的实用性和正确性。
Process analysis and planning which influences the quality of productions, costs, efficiency and the mould life is one of the core steps in the development of productions for automobile panel. With the development of automotive industry, traditional process planning has not met the requirement of productions in high quality. In recent years, with of the development of computer hardware and computer graphics, as well as the theory of finite element, the numerical simulation of sheet metal forming is gradually a tool of process analysis and optimal designs.
This research is supported by NSF and named as:“The Independent Research of High-speed Simulation and Optimal Process Design aiming at the Formability of Automobile Panel”(NO.50575080).
Based on the software of FASTAMP, which is developed on dynamic explicit algorithm by State Key Lab. of Material Processing and Die & Mould Technology of HUST, An algorithm for open cutting is presented and realized for mesh adaptive technique by using computer graphics and the theory of finite element, at the same time, an algorithm of mesh generation for sheet metals is realized based on mesh generation in the open cutting method.
An algorithm for open cutting is presented for mesh adaptive technique, and the template library based on mesh adaptive is built. Elements which are passed by trimming line are adjusted by using advancing inciting and adjustment method. The transmission of physical information is completed by mapping method. This algorithm is integrated into the software FASTAMP which is based on dynamic explicit method. The simulation of a practical automobile body metal sheet is presented, in which the size, position and shape of the open cutting and the distance of the die when the open cutting is processed are optimized. This optimized plan is applied in the production, the precision of the numerical result and the practicability of the algorithm for open cutting are validated by this experimental result.
On the basis of the idea of mesh generation in the open cutting method, a new algorithm of mesh generation for sheet metals is presented. The minimum bounding area of the shapes of the formed sheet metal is built, and this area is zoomed in properly. Mesh of quad-elements is generated in the amplificatory area. According to the outline of sheet metal, gird in this area is adjusted by use of open cutting method, at the same time, the elements in the peripheral area of the outline of sheet metal are deleted, and the numbers of elements and nodes in the inside area of it are numbered. Finally the validity and the practicability of this algorithm are validated by many experimental results.
本课题来源于国家自然科学基金项目:面向自主设计的汽车覆盖件成形性快速仿真及工艺优化技术研究,项目批准号为50575080。在华中科技大学模具国家重点实验室开发的基于动力显式算法的FASTAMP软件的平台上,运用计算机图形学技术和有限元理论,提出并实现了基于网格自适应加密与减密的工艺切口算法,实现了初始板料网格剖分算法。
本文深入地研究了求解板料成形问题的动力显示算法中的一些关键技术,包括板料成形动力分析的BT(Belytschko-Tsay)壳单元数学模型和由单点积分引起的零能模式的解决方案;重点介绍了网格自适应加密与减密技术,包括该技术的判断依据,单元的加密算法,单元的减密算法和加密或减密后单元的物理场量的继承关系;较为简单地介绍了动力分析显式求解方法以及该算法的稳定条件。
本文通过对多种工艺切口算法进行研究比较,分析了它们的优缺点,提出了一种新的面向网格自适应加密与减密的工艺切口算法,建立了加密网格剖分模板库。算法采用向前推进方式对切边线经过的单元进行网格调整,通过网格映射方法完成新旧单元体系下物理量信息传递。将算法集成到基于动力显式算法的FASTAMP软件中,选取实际生产的汽车覆盖件进行成形模拟,优化了工艺切口时的模具行程,以及与切口相关的参数,例如切口的大小、位置和形状。将工艺切口方案应用于实际拉深成形中,其成形结果不仅验证了数值模拟结果的准确性,同时也说明工艺切口算法的实用性。
本文根据工艺切口模拟算法中网格调整的思想提出了一种新的平面网格剖分算法。建立了板料轮廓的最小包容区域,以该区域进行适当的放大,在放大的区域内进行四边形单元网格的划分,根据板料轮廓线对放大区域的网格进行调整,删除板料轮廓线外围单元及其上的节点,并对轮廓线内围单元的单元号和节点号进行重新编号。最后通过许多实际用例验证了本算法的实用性和正确性。
Process analysis and planning which influences the quality of productions, costs, efficiency and the mould life is one of the core steps in the development of productions for automobile panel. With the development of automotive industry, traditional process planning has not met the requirement of productions in high quality. In recent years, with of the development of computer hardware and computer graphics, as well as the theory of finite element, the numerical simulation of sheet metal forming is gradually a tool of process analysis and optimal designs.
This research is supported by NSF and named as:“The Independent Research of High-speed Simulation and Optimal Process Design aiming at the Formability of Automobile Panel”(NO.50575080).
Based on the software of FASTAMP, which is developed on dynamic explicit algorithm by State Key Lab. of Material Processing and Die & Mould Technology of HUST, An algorithm for open cutting is presented and realized for mesh adaptive technique by using computer graphics and the theory of finite element, at the same time, an algorithm of mesh generation for sheet metals is realized based on mesh generation in the open cutting method.
An algorithm for open cutting is presented for mesh adaptive technique, and the template library based on mesh adaptive is built. Elements which are passed by trimming line are adjusted by using advancing inciting and adjustment method. The transmission of physical information is completed by mapping method. This algorithm is integrated into the software FASTAMP which is based on dynamic explicit method. The simulation of a practical automobile body metal sheet is presented, in which the size, position and shape of the open cutting and the distance of the die when the open cutting is processed are optimized. This optimized plan is applied in the production, the precision of the numerical result and the practicability of the algorithm for open cutting are validated by this experimental result.
On the basis of the idea of mesh generation in the open cutting method, a new algorithm of mesh generation for sheet metals is presented. The minimum bounding area of the shapes of the formed sheet metal is built, and this area is zoomed in properly. Mesh of quad-elements is generated in the amplificatory area. According to the outline of sheet metal, gird in this area is adjusted by use of open cutting method, at the same time, the elements in the peripheral area of the outline of sheet metal are deleted, and the numbers of elements and nodes in the inside area of it are numbered. Finally the validity and the practicability of this algorithm are validated by many experimental results.
引文
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[8]柳玉起、李志刚、杜亭等,在汽车覆盖件及其工艺设计中的应用,机械工人冷加工,2006,4:18-21
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[3]余雷,袁国定,岳陆游.有限元数值模拟在汽车覆盖件设计和制造中的应用.锻压技术,2002,2:23-26
[4]梁炳文、胡世光.板料成形塑性理论.北京:机械工业出版社,1987
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[6]王祖唐、关延栋、肖景容.金属塑性成形原理.北京:机械工业出版社,1999
[7]于汇泳、祁文军、李昌雪,有限元数值模拟技术在汽车冲压成形中的应用,现代制造工程,2005(增): 71-73
[8]柳玉起、李志刚、杜亭等,在汽车覆盖件及其工艺设计中的应用,机械工人冷加工,2006,4:18-21
[9] Fouad EL KHALDI , Marc LAMBRIKS. New requirement s and recent development in sheet metal stamping simulation. Proceedings of the NUMISHEET’02 Jeju Island , Korea , 2002 , 10 , 411～421
[10] Denise Burgarellia, Mauricio Kischinhevskyb, Rodney JosuéBiezunera, A new adaptive mesh refinement strategy for numerically solving evolutionary PDE’s, Journal of Computational and Applied Mathematics, V196(1),2006, P115-131
[11] Frans Pretorius and Matthew W. Choptuik Adaptive mesh refinement for coupled elliptic-hyperbolic systems Journal of Computational Physics, V218(1),2006, P246-274
[12] G.S. Palani, Nagesh R. Iyer and B. Dattaguru, New a posteriori error estimator and adaptivemesh refinement strategy for 2-D crack problems,Engineering Fracture Mechanics, V73(6), 2006, P802-819
[13] Marcal P.V.,King I.P.,Elastic-Plastic Analysis of Two-Dimension Systems By the Finite Element Method, International Journal of Mechanical Science, 1967, Vol. 9: 143-155
[14] Hibbit H.D., Marcal P.V.,Rice J.R. A finite element formulation for problems of large strain and large displacement, International Jorunal of Solids and Structures, 1970,Vol.6:1069-1071
[15] Wang N.M.,Budiansky B. Analysis of sheet metal stamping by a finite method, Journal Applied Mechanics,1978,45(1):73-82.
[16]温宏宇,娄臻亮,阮雪榆.基于无网格法的板料成形数值模拟的研究探索.锻压装备与制造技术,2004,29(4):98～100
[17]柳玉起.计算机模拟在金属成形行业的应用和发展现状.锻造与冲压,2005,6: 16, 18,20,22
[18]黄菊花,董湘怀,肖祥芷.板料成形有限元模拟网格重划及其应用.锻压机械,2002, 2:47～49
[19]崔青玲,李长生,刘相华等.无网格法及其在金属塑性成形中的应用.塑性工程学报.2005,12(1):38～42
[20]温宏宇,燕存良,娄臻亮,阮雪榆.无网格法分析板料成形过程的关键技术及难点.模具技术,2005,3:11～13
[21] Onate E ,G arino G C ,etc. NUMISTAMP: A research project for assessment of finite element models for stamping processes. NUMISHET'93,Is ehara,Japan,1993:19-33
[22]李光翅.三维板料成形过程的显式有限元分析.计算结构力学及其应用,1996,13(3): 253-268
[23] Coelho P .J, Argain J .A local grid refinement technique base upon Richardson extrapolation [J] Appl. Math.Modelling,1997,21:427-436
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