The Research Of The Method For Object-Oriented Nonlinear Finite Element Programming

Typical finite element programs, which were designed basing on the idea of procedural programming, consist of thousands of lines of procedural codes. The codes contain many complex data structures which are accessed throughout the program, and these global data structures make the flexibility of the program system low. Since the Procedural-Oriented programming language based on the idea of procedural programming can't supply programmer with data abstraction, data encapsulation and etc., more and more latent problems such as low code reuse rate, complex debugging and long developing period appeared during developing and maintaining finite element programs. These problems limited the designing of nonlinear finite element programs, and designing process will be faced with the difficulties not only caused by nonlinear but also caused by designing process itself. So, in the practical engineering application, it's necessary to produce a new design method into finite element programming. The object-oriented method is the right method which can improve the efficiency of the design, and programs based on it are more maintainable and more expandable. In the recent decade, more and more researchers have stepped into the field of object-oriented finite element programming to seek for the best combination of object-oriented methodology and finite element programming. Under these backgrounds, the deeper research of object-oriented nonlinear finite element programming is conducted.The abstraction and encapsulation of the basic data in this dissertation have been accomplished by utilizing some constructed and applicable classes offered by other researchers. Furthermore, the research has put great emphasis upon the implying relationship among the basic classes, and has formed highly cohesive FEFC (Finite Element Foundation Classes). The construction of FEM Application Framework is determined by FEFC which provide framework and interface for the subsequent design of nonlinear finite element programs. The validities of FEFC and FEM Application Framework have been confirmed by the process of the example program.Data abstraction and data encapsulation are the basic concepts of the object-oriented method. To abstract and encapsulate the basic data classes has been the virtual basic work in the field of the object-oriented finite element programming. Analyzing the signification of the single data class and the relations among the data classes, the existing basic data classes were integrated, and the concept of FEFC was presented, which is similar to MFC encapsulated by Microsoft Company. The hierarchy of FEFC was given in this dissertation. The presentationand design of FEFC increases the condensability among the basic data classes, and the relation among the data classes was established via the bottom codes. FEFC guarantees that the data can communicate via the form of messages, and reduces the probability that too much complex global data structures be designed in a finite element program. So, the flexibility of the finite element program was improved basing on FEFC. Moreover, FEFC forms the base of the FEM Application Framework.The subsequent research focuses on the construction of a frame tool for nonlinear finite element programming. According to the theory of nonlinear FEM and the feature of nonlinear FEP, the FEM Application Framework was constructed based on FEFC associated with nonlinear solution algorithm. The construction of FEM Application Framework applies fixed skeletal codes for nonlinear FEP, and subsequent design of the program can communicate directly with the interface offered by the skeletal codes, then, the efficiency of the programming increased in this way. Furthermore, the modification of programs was separated with the main system to reduce the cost of the program maintenance. Designing different kinds of nonlinear FEP will be convenient using the application framework, and object-oriented technique ensure programs can be expandable well.Finally, a practical nonlinear finite element program which conc...