Extensibility of finite element class systems: a case study

The paper deals with the robustness and extensibility of class systems for finite element analysis. The extension of an existing system designed for linear elastic problems to handle non-linearity is used as a case study. Only one substantive change was required to the existing classes in order to extend the system. The other changes involved the addition of new classes, and in these the additional code required was close to the minimum possible. The system does rely heavily on controlled typecasting. Therefore, an alternative system was developed which used iterators. This produced a system that did not require typecasting. The use of the object-oriented approach also allowed sub-structure based algorithms to be implemented in a straightforward manner, and thus to implement more flexible and efficient algorithms.