Research On The Key Technology Of Adaptive Quadrilateral Mesh Generation In The Numerical Simulation Of Fineblanking

As fineblanking's wide application in different industries, such as auto mobile, aircraft and general mechanicals, the finite element analysis of fineblanking is playing a more and more important role in the process from design to manufacture. Mesh generation is also one of the key techniques of fineblanking numerical simulation. It is well known that fineblanking is a complex process, a kind of large displacement, large rotation, and large strain plasticity forming process. In order to ensure the calculational precision as well as reduce calculation time, adaptive mesh generation is put forward, and it is also well known that adaptive mesh generation is a hot research project in finite element technology field. In terms of fineblanking's process features, in this thesis a deep and systematical research into mesh generation is made, and an adaptive quadrilateral mesh generation method which is suitable for fineblanking simulation is proposed, and the correspondent program is also developed. The main contributions of the paper are given as follows:Combining Paving and Looping methods, a new modified finite element mesh generation method is proposed. The method not only takes advantages of Paving which can generate a high quality boundary element layer, but also adopts the advantages of Looping which is well geometry adaptation, high speed and high inner mesh quality. Beside taking full advantages of the two methods, some modifications are made to improve the weaknesses in the original methods, solving the problem that mesh can not be generated in the long and narrow zone, improving the original algorithm which is used to calculate the number and spacing of new generated nodes along the splitting line, and also trying to generate two boundary layers by Paving to verify whether the boundary elements can be further improved.Boundary adaptation and specified area mesh refining. Based on the study of adaptive mesh generation algorithms and mesh refining methods, according to the features of fineblanking, a boundary adaptive method with a point-by-point insertion method is adopted and a primary research on the specified area mesh refining is also made.An improved algorithm for graded meshes smoothing. Smoothing algorithms like Laplace tend to equalize the size of local elements to mean size. It is no doubt that it will redistribute nodal density and affect the simulation precision. Aiming at solving these problems, a modification of Giuliani algorithm, which is special for graded meshes smoothing by eliminating the elements equalization influence by the mean height and basis of the triangles in the original algorithm, is presented in this paper. Also element distortion volume, element area changed ratio and compound element quality assessment factor are proposed to assess the results of the samples in this paper. The results confirm that the modified algorithm can not only improve the meshes quality greatly, but also decrease the influence of the elements size gradient.Based on Visual C++.NET 2003, the corresponding programs are developed.