R. Foerch and J. Besson Accepted in Computer Methods in Applied Mechanics and Engineering .
Abstract
This paper discusses the aspects of object oriented finite element design which become relevant as the project size increases. A simple core library is described which aids program development by isolating repetitive tasks into optimized classes. This library addresses particularly the mathematical entities which appear in mechanics. Several object oriented class idioms are given as well, with implementation syntax in C++. The classes address the reduction of interdependence in the code project, and facility expandability in the long-term. Application of these abstract programming techniques are given within the context of a complete, working FEM code design which employs the object techniques thoroughly on every level of the computation. Furthermore, suggestions are given on how to reformulate problems in an object oriented fashion in order to plan on expandability. Results for CPU performance are given with respect to a Fortran code, but are seen to have very limited real relevance.
R. Foerch, J. Besson, G. Cailletaud, and P. Pilvin. Accepted in Computer Methods in Applied Mechanics and Engineering .
Abstract
This work presents an object-oriented design approach to the programming of finite element constitutive equations. A universal interface for arbitrary material laws is introduced from which easy addition and expansion of the material library can take place. Although such expansion using a generic interface is by definition polymorphic, the idiom is carried much further in several aspects of program design. Deriving from abstract examples of equation and algorithmic encapsulation, simple elastic damage and complex inelastic constitutive laws are developed. Examples of calculations show that adequate performance is given by C++ with respect to Fortran77 for simple to very complex material laws. The performance is seen to be a much stronger function of the compiler used than the actual numerical complexity.
M.R. Julien, R. Foerch, M. Aubertin and G. Cailletaud. Presented at the 4th Conference on the Mechanical Behavior of Salt, Montreal, Canada, June 17, 18 (1996).
Abstract
A unified constitutive model using internal state variables (ISV) to describe the inelastic behavior of salt in the ductile and semi-brittle regimes has been implemented into a 2D/3D object oriented finite element code (Zebulon). This program was specifically designed for the analysis of complex material behavior under a variety of loading conditions, including cyclic and non-isothermal loading. The constitutive model (SUVIC-D) is composed of a viscoplastic and a damage component. The viscoplastic component implementation has been done for both explicit and implicit integration methods. Damage has so far been done only with the explicit scheme. This paper presents some details of the implementation, a discussion about the integration techniques, and numerical simulations of experimental results for artificial salt using both the viscoplastic and the damage components. The results show that the extra effort in implementing the implicit integration scheme is worth the effort since it allows an improved convergence for load control conditions.
Object oriented FEA