In this paper, the problem of parallelizing the finite element method for distributed memory computers using domain decomposition methods is addresed. We focus on direct domain decomposition methods because they are robust and well adapted to multi-level decompositions. Two important problems concerning these methods are studied: the condensation of subdomains and the resolution of the interface problem. Finally, the results are presented which show that, in sequential implementation, direct decomposition methods are more efficient than standard LDL^T-skyline solvers, and compare favorably with state-of-the-art LDL^T-sparse solvers.

M. Kaminski. Homogenization in elastic random media. CAMES 1996 (3)

The theoretical foundation and a numerical procedure of deriving stochastic effective properties of linear-elastic periodic fibre composite are presented. Using Monte-Carlo method, a Fortran program based on the deterministic rectangular plane strain element of the Finite Element Method has been worked out to evaluate probabilistic density functions of these properties. The expected values of elastic effective characteristics thus obtained are compared with deterministic results of COSAN modelling.

E. Rusinski, A. Wall and R. Sobolewski. Finite element analysis of fractured tibia treated with ZESPOL stabilizer. CAMES 1996 (3)

Some aspects of applying the external stabilization method to the treatment of selected cases of tibia fractures make the subject of this paper. ZESPOL, used as an external stabilizer, was selected from among many other methods. In order to define the state of deformations and stresses existing in a fractured tibia stabilized with ZESPOL, an unconventional quantitative model was prepared. Finite element analysis was applied to the strength analysis of the whole system. Some final results and computations are presented.

E. Brauns and J. Patyn. Calculation of Weibull life expectancy parameters from fracture data using the maximum likelihood criterion and a Nelder-Mead simplex minimisation algorithm. CAMES 1996 (3)

This paper describes a mathematical technique to calculate the model parameters for a classical Weibull statistic. This type of statistic can be applied in a number of life time expectancy problems. A typical example is the brittle behaviour of components produced from technical ceramics. A Nelder-Mead simplex algorithm is introduced to obtain the Weibull parameters using the maximum likelihood criterion. Program code for a Matlab for Windows environment is presented.

S. Kaliszky, G. Popper, J. Lógó and G. Károlyi. Identification of bilinear material models of nonlinear beams on nonlinear foundation. CAMES 1996 (3)

In the analysis of the problem the beam is modelled by hinge elements connected together by rigid bars while the foundation is replaced by spring elements supporting the hinges. The nonlinear behaviour of the beam and the foundation is described by specially formulated bilinear material models. The characteristics of these models are considered to be unknown but, on the other hand, the deflections of certain points of the beam are given. The goal of the investigation is to determine the best values of the material charcateristics by the use of a mixed variational principle based on the bilinear material model and by the application of the identification methods. The problem is stated in the form of constrained, nonsmooth, nonlinear mathematical programming problem, and the identification is equivalent to finding the minima of a non-linear, multivariable functional. The application is illustrated by the solution of an example.

H.A. Dieterman and R.R. Gajewski. An improved viscous boundary for dynamic soil-structure interaction. CAMES 1996 (3)

In many engineering problems modelling of wave propagation in infinite or semi-infinite domains is of great importance. One of the main limitations of the usage of the finite element method in dynamic soil-structure interaction arises when it is used for the modelling of an infinite domain. If nothing is done to take care of artificial reflections at the mesh boundaries, errors are introduced into the results. To handle the reflections different artificial boundaries have been proposed in the literature and used. This paper deals with an improvement of one of the most widely used local absorbing boundary condition - the standard viscous boundary. Both analytical investigations of the efficiency of the boundary as well as numerical results are presented.

R.R. Gajewski and T. Kowalczyk. A prototype object-oriented finite element method program: Class hierarchy and graphic user interface. CAMES 1996 (3)

The paper concerns the application of an object-oriented approach to the development of FEM software. A brief introduction to basic concepts of object-oriented modelling is given, followed by a short overview of developed classes. Objects, classes, methods and inheritance are illustrated using a graphical representation. The design, implementation and maintenance of an object-oriented program is compared to that of an equivalent procedural program in order to identify advantages of the object-oriented approach. Some design problems of conventional finite element analysis software and their possible solutions offered by the object-oriented methodology are identified and discussed.