Theory Of Sectional Optimization For Membrane Structures And Software Secondly Development In MSC.Nastran

The sectional optimization theory of membrane structure under size, stress and displacement constraints is developed. A special optimization module is developed by using PCL language of MSC.Patran. The ratios of the design thickness and the initial thickness of membranes are used as design variables, the design variables are made connected with constraints and object function. Full stress criterion is used to settle size and stress constraints problem. Using the library functions of MSC.Patran language the stresses of structural elements is picked up, and the maximum stress of the elements controlled by the same design variable is found. Finally the member thickness is got according the relation of stress and variables. From the "structural analysis --getting the thickness of the later step--structural analysis" circulation, the last optimum thickness of member is got.To multi-constraint problem about size, stress and displacement, the size and stress constraints are transformed into the movable size constraints. Then using the method of unit virtual-load, the displacement constraints are transformed into a explicit function to the design variables. Dual mathematical programming is used to map the original problem exactly and the second approximation of the dual problem is set up by Taylor's expand form, it is solved by QP (quadratic programming) solving device. In the process of programming, the scaling step is adopted to adjust the performance and efficiency of optimization, using the method of filtering inactive constraints to reduce the sensitivity analysis. Using the active and inactive variables alternation to ensure the convergence stability. At last, some examples and their results compared with MSC.Nastran's are used to examine the program. The reliability, the accuracy and the high-efficiency of the program are verified.The user interface is established that connects with the interface of MSC.Patran by using the library functions of MSC.Patran. The visualization of the program is realized. Engineers only need to input optimization design parameters, such as the values of the size, the stress and the displacementconstraints, the optimization design precision and the safety factor in the interface, and then push the "Apply" button, all will be OK.