Theory Of Sectional Optimization For Plate And Shell Structure And Its Secondly Development Of Software Based On MSC/NASTRAN Program

On the premise of a given set of material parameter, structural boundary shape and condition, design variables-thickness of plate and shell, is designed to minimize the structural weight subjected to the constraint conditions. 1.For the problem with size and stress constraints, full stress design method is used to solve the sectional optimization of plate and shell structures. Before the optimization modeling, the scaling step technique is used to adjust the structural behavior, and the stability of computational convergence is ensured.2.For the problem with size, stress and displacement constraints, the stress constraint is transformed into movable lower bounds of sizes, the displacement constraint is transformed into an approximate function which explicitly includes design variables by using Mohr integral theory. A mathematical programming model of the optimization problem is set up. The dual programming of the model is approached into a quadratic programming model. Finally, the Lemke algorithm is used to get the design result which satisfies the size, stress and displacement constraints.Based on MSC/NASTRAN software, by using of PCL language (PATRAN Command Language), new software of optimum design module was secondly developed for sectional optimization of plate and shell structures. Visualization is realized by setting the menu into PATRAN. Users can define design variables, constraint conditions and objective function by the iterative function of computer interface.Some numerical examples of optimum design verified the credibility, validity and speed convergence of the program.