Design Optimization Of Stiffened Shell Structures

Stiffened plates and shells are widely employed in engineering because their high strength to weight ratio, so the design of stiffened built-up structures is important. With its widely applications, stiffened shell structures are becoming more and more complicated and the number of design parameters which affect its structural performances is being increased. Engineers are facing much more difficulties when designing such kind of structures. Therefore it is very essential to find a high efficiency and feasible method for the optimum design of stiffened shell structures by using conventional finite element software, such as MSC. Nastran.Based on the five optimization methods employed by MSC. Nastran, in conjunction with the artificial density approach for topology optimization, the stiffeners layout optimization method is presented. In the method, size design optimization problems which include sectional dimensions of stiffeners and shell thickness distribution can be taken into account at the same time. Numerical examples are presented to validate the effectiveness of the method. With the employment of this method, structural performances can be greatly improved. The investigation develops a convenience and feasible method for the design optimization of stiffened shell structures. The thesis is arranged as follows:In chapter 1, Design optimization methods of structures and the theories of optimization algorithm in MSC. Nastran are summarized;In chapter 2, The bdf files of the MSC. Nastran software are introduced, and numerical examples with the different structural response as the object function are presented;In chapter 3, The method for layout optimization for stiffeners is proposed. Numerical examples are presented for the detail investigations for the method;In chapter 4, The application of the method to design optimization of a stiffened storage tank is presented;In chapter 5, The application of the method to the design optimization of a spacecraft stiffened structures is presented.The research of the thesis is supported by the National Natural Science Foundation of China (10421202).