Shape Optimization Theory For Truss Structure And Secondly Development For Software Based On MSC/NASTRAN

For shape optimization of truss structure, the design variables are separated into two kinds of bar sectional size and nodal position by multilevel decomposition optimization method. The solution process is divided into two steps. At the first step, supposed all nodal positions are unchangeable. The bar sectional sizes are optimized to make the weight of the structure minimized under constraints of stress, displacement and local stability. At the second step, supposing the active displacement constraints of the first step keeping unchanged. A quadratic programming model that increases the structural rigidity is solved. The obtained new nodal positions don't increase the value of the objective function under the constraints. The two steps alternatively executed until convergence.By using MSC PCL (PATRAN Command Language), secondly development has been accomplished to integrate the decomposition optimization method into the optimization module of MSC/NASTRAN software. The implementation of decomposition optimization and the integration analysis of MSC/NASTRAN in optimization shorten the computing time of optimization, decrease the work intensity of designer and improve optimization efficiency greatly. Furthermore, visualization is realized by setting the menu into PATRAN. The users can define design variables and attain the optimization of objective function under the constraints condition by the alternative function of computer interface.The feasibility and effectiveness of　the algorithm are verified by truss examples. Several numerical examples are used to testify the convergence efficiency of program.