Structural Optimization And Nonlinear Finite Element In The Breech Closed Gas Structure In The Applied Research

Application of structural optimization and nonlinear finite element technique to nonlinear multi-component structural system (assembly) is studied for the sake of the obturator of the breech mechanism of an automated mortar. The method and technology for optimizing nonlinear multi-component structural system with contact is mainly researched in this thesis.The main research work is composed of the followings: 1) A new method for optimal design of nonlinear multi-component structural system (assembly) with contact is put forward in this thesis. By combining Genetic Algorithm with parameterized geometry and finite element model of structure, optimization of the parameters of nonlinear multi-component structural system with contact can be accomplished through the programming environments of secondary development on a universal integrated CAE platform (MSC.PATRAN + MSC.MARC). 2) Theory and fundamental of Genetic Algorithm and finite element method is expounded. 3) A 3-D geometry and finite element model of the assembly of the obturator of the breech mechanism is established. Quasi-static and dynamic finite element analysis of stiffness, strength and obturating performance of the obturator of the breech mechanism is carried out, based on elastoplastic theory and multi-body contact algorithm, and the simulation results coincide with experimental results, further, the effect of friction factor on its obturating performance is investigated. 4) The method for rapid implementation of parameterized modeling of geometry and finite element of structure through a universal CAE software(MSC.PATRAN) is researched, and parameterized modeling of the obturator of the breech mechanism is accomplished using the method. Graphical user interfaces are developed to be convenient for implementing of parameterized model and debugging of program parameters. Program of optimization based on GA is designed to optimize obturating performance of the obturator of the breech mechanism, further, the effect of control parameters of GA and friction factor on the optimal structure is studied. 5) The 3-D geometry and finite element model of the assembly of the optimized obturator of the breech mechanism is set up in terms of the optimized structural parameters. Quasi-static and dynamic finite element analysis of stiffness, strength and obturating performance of the optimized obturator of the breech mechanism is performed. Comparison of stiffness, strength and obturating performance of the initial obturator of the breech mechanism with those of the optimized one is made, which indicates that the stress concentration that leads to fatigue failure in theoptimized structure is eliminated. The flexibility of the optimized obturator of the breech mechanism is considerably increased and its obturating performance is substantially improved. The optimization objective is obtained.Success in optimizing the obturating performance of the obturator of the breech mechanism shows that the method and technology for optimal design of nonlinear multi-component structural system with contact put forward in this thesis is effective and practical. Structural optimization problems that are difficult to solve through the optimization method available in the universal CAE software can be accomplished by means of this method.