Research Of Hybrid Stress FEM And Its Integration With MSC/PATRAN

Computational Mechanics is the basic of CAE(Computer Aided Engineering), because of the rapid development of computer technology, it becomes one of the most important ways to resolve engineering problems. Since FEM is very easy to be written into computer programs and widely effective to most kinds of mechanical problems, FEM has been developed very quickly under the requirements of industry since its concept appeared in 50's last century. Based on Hu-Washizu variational principle, T.H.H. Pian presented mix FEM and hybrid FEM in 1964. For its good capability in solving the irregular elements problems, incompressible material problems, and high precision in stress and strain results, the research of mix and hybrid FEM is in the ascendant. This paper contains two parts of work: the construction of functions for some new hybrid stress elements, and the practical application of FEM.In chapter two of the first part, we give the new axisymmetric hybrid stress optimization function using the Wu-Pian-Huang optimization theory, modify the former function published by T.H.H. Pian, Wu Changchun etc. Through the numerical example it's easy to get the conclusion that the new axisymmetric hybrid stress finite element we present in this paper has better precision in the results of displacement and stress. Then we apply the method of incompatible FEM and hybrid stress FEM into axisymmetric problems of transversely isotropic material. With the penalty equilibrium optimization method, we find a new hybrid stress element special for axisymmetric problems of transversely isotropic material. After several numerical examples, the conclusion is made that the hybrid stress finite element with penalty equilibrium has the best capability among all these elements. After that in chapter four, a axisymmetric hybrid stress finite element for piezoelectric media is presented on the optimization condition for the coupling of electrical and elasticity. It's practicable and rational in the numerical example. In the fifth chapter, we study the p-version hybrid stress FEM. The numerical example shows that if we use the correct Guess integral, this method will give right answer. It has good performance for both p-version and hybrid stress FEM. Last, a hybrid stress finite element with second stress completion is presented, which keeps the virtue of normal hybrid finite element, especially good for incompressble material, because it can avoid the self lock of displacement and instability of stress results.In the second part, two methods are presented in order to simplify the pre-procession and post-procession of FEA in the seventh chapter, to integrate the hybrid stress element program into MSC/PATRAN which is one of the best commercial programs for pre-processing and post-processing FEA. It can give very good user interface and reduce the cost in pre-procession and post- procession. It also provides several intuitionistic ways in the post-procession. Last we give some engineering examples of FEM to show the up to date advancement of CAE programs, and also give the directions to the application of FEM in practical work.This paper includes two parts of work-the construction of some new hybrid stress elements'functions, and the practical application of FEM. It's helpful for the research and application of hybrid stress finite element method and integration the private FEM programs with the commercial program system. It's also helpful for the application of FEM in engineering problems.