(Using The Object Oriented Technology To Develop The Finite Element Analysis Program For Nonlinear Problems)

Usually structured approach is adopted in the conventional finite element software development, using Fortran language. Currently computational mechanics softwares are faced with demands of extension, while traditional process-oriented design makes softwares’ maintenance and expansion difficult, which to a large extent hampers the development of finite element softwares. In order to overcome the design drawbacks, researchers all over the world start to use the object-oriented programming method. Nowadays, most of the commercial numerical simulation softwares generally adopt object-oriented method to develop new modules and rewrite the existing modules.In this thesis, both the theoretical framework and programming skills about solid mechanics are introduced. Firstly, the basic knowledge are systematically summarized according to the process of nonlinear finite element analysis, including the establishment and solution of the general equations. Mainly it summarizes the derivation of strain matrix B under small and large deformation, tangential matrix D of several typical materials, the overall load and the three main solving strategies. And also, comparative analysis is made between the three methods.In general analysis, each component of structures consists of only one kind of material. If each component is defined as a domain, then each domain simply saves an elastic matrix, and initial stress method and the initial strain method can take full advantage of this design. In this thesis, solid and truss elements are distinguished, and also domains are divided to truss and solid types. This division pattern unifies element operations of the same type of domain and provides an alternative structure for programmers. In practical use, the number of domains depends on the defined material number.In programming practice, this thesis provides a new numbering mapping strategy for nodes with different degrees. This method determines the degree of a node according to the elements it attaches to, and completely eliminates the zero columns and lines which improves the computational efficiency. In order to facilitate the realization of multi-step loading, a new type LC is designed which includes all the constraint and load information. Additionally, a special tensor class is designed, which is usful in hyper-elasto material numerical simulation.