Research On Algorithms For Open Cutting And Mesh Generation For Sheet Metals

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.