Keywords: finite element software, object oriented FEM.

In a recent years, the research community is facing to a growing demands to merge the power of current computer technology with the extensive knowledge acquired in engineering, mathematics, physics and other disciplines, and to effectively exploit them in the design of new multi-functional materials and structures. These growing demands for realistic modeling that typically includes state-of-the-art constitutive models, adaptive and multi-level solution techniques brings in new software issues.

The paper presents design principles and structure of object-oriented finite element software OOFEM [1], which is being actively developed for several years. The main advantages of the presented framework include modular design, extensibility, and robustness. The code itself is freely available and is distributed under GNU public license. It provides tools for linear and nonlinear analysis of mechanical and transport problems on sequential and parallel machines. Particular attention will be given to the description of problem representation and its numerical solution, and to the design of material-element frame, because of their fundamental importance.

The overall structure will be presented graphically using Coad-Yourdon methodology. Such representation allows to show class hierarchy as well as the mutual relations between the classes, representing the generalization/specialization, whole/part, or association relations. All the fundamental abstract base classes, representing basic building blocks of finite element code, will be introduced and their role will be discussed.

The problem description frame describes the formulation of the problem, its numerical solution and data storage. The conceptual design of this frame will be presented with respect to the important issues, such as independent problem formulation on numerical solution and data storage, adaptivity, multi-physics problems, and interfacing with external libraries.

The material-element frame contains the abstractions for finite elements, constitutive models, integration points, etc. The design has been focused to general and modular structure allowing to accommodate any constitutive or cross-section model and to provide specific support for nonlocal materials of integral type or micro-plane based materials, for example.

In the final part of the paper, the overview of the current code capabilities will be summarized and the future direction of code development will be previewed.

1

OOFEM project page, http://oofem.org, 2003.

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