Theory Of Shape Optimization For Two Dimensional Structure And Its Secondly Development Of Software Based On MSC.NASTRAN Program

A program of shape optimization for two-dimensional continuum structures , which is carried out on MSC.PATRAN&NASTRAN panel, is described in this thesis, according to a two-phase control theory presented by Professor Sui yunkang , the optimization is treated as a Sequential Quadratic Programming problem.The research of shape optimization in this thesis focuses in the region of modelling of optimization, incorporating the advanced theory of optimization, general analysis software and the model of the various finite elements, with the purpose of meeting the urgent need of engineers.There are three difficulties in shape optimization: the first one is the relation between design variables and objective function, or between design variables and constrant function is not easy to find the simple apparent relation and the sensitivity. The second one both the structure shape describing and the shape changing control is difficult. The third one is that the mesh should be generated and changed automatically in the procession of optimizing.Two-phase control indicates that we can insert two mid-variables between objective function and design variables, which are the keypoints and nodes in the mesh. Thus we can form the two-layer control relation about control keypoint of design variables and control node(mesh) of keypoint, and solve the sensitivity problem effectively. By using the design unit and keypoint, a change of structural shape can be controlled and described precisely. Use the MSC.PATRAN to form the initial mesh, then control the mesh in the procession of optimizing using mapping method. Therefore, the difficulties can be solved by applying the Two-phase control method.The development of shape optimization module on MSC.PATRAN is implemented on the base of PCL language. Furthermore, the function of shape optimization for two-dimension continuum structures is augmented. The advantages of this program lie in incorporating the mighty function of the famous structure analysis software, mature handling interface of pre-process and post-process, convenient and usable finite element modelling theory and advanced optimizing theory.The idea of the research is verifed by some examples. And the reliability, the accuracy and the high-efficiency of the program have been testfied by the results of the exams.