Harald Tägnfors

Visualization of FE-data, interactively and on video

Abstract This article presents a computational environment for visualization of FE-data and video production. The general ways to visualize FE-data are discussed and software suitable for building visualization applications are described. The pitfalls and considerations to be taken in video production are pointed out and described. The procedure in video editing is exemplified for one system.Two applications of animations are described. One has been developed to get a deeper insight and understanding of how a 3D mesh generator works. The other is a presentation of results from a time-stepping procedure of a wave propagation problem on video. The tools we have chosen for our visualization system are AVS (Application Visualization System) from AVS/UNIRAS, and Video Machine from FAST.

Aspects on Methodology for FE-Program Development

There is a great need for a systematic approach to the development of Finite Element (FE) programs. This paper describes the reasons for such an approach and gives examples on general methods which have been developed for certain steps in the program development process. A selection of methods, along with rules how to apply them, constitutes a methodology. The special features in the FE-method which have to be considered when selecting methods in a methodology for FE-program development are discussed as well as the possibilities to support the methods with tools. The author also presents an architectural design of a FE-program with modules in seven hierarchical levels, where control of calculation can be switched between the Program Developer and User in a flexible way.

Estsol—a subroutine library for establishment and solution of linear equation systems

One of the crucial steps in the solution of problems with Finite Element Methods is establishment and solution of systems of equations. A numerous number of papers have been presented concerning different techniques of solution of equation systems such as direct methods, Mondkar and Powell, 1 Wilson, 2 Kamel and McCabe, 3 Argyris and Br6nlurid, a and iterative methods such as conjugate gradient, Axelsson and Gustafsson, s Gustafsson and Lindskog, 6 and viscous relaxations, Hughes et al., 7 Zienkiewicz) However, the user of these methods normally has to write a number of subroutines for the establishment and solution which are different for each method. The presented subroutine library will establish and solve a linear system of equations for a number of right-hand sides using almost the same data for all methods. It provides the user of an application program with the possibility to select the solution method which is best suited concerning efficiency and accuracy for the problem at hand. The subroutine library presented here covers both the establishment and the solution and is supported by a data base management system (DBMS). Several direct and iterative methods may be chosen. Independent of which method is to be used at the solution the required data is the same. The subroutine library is a part of the programming system SITU, T~ignfors et al., 9 which is both a tool for program development and an assemblage of engineering programs. A program developer only has to calculate required data in a space provided by the data base management system, which in this version is PRISEC, T/ignfors et al. 1° A program developer first has to assure that some arrays containing information about topology are available and then call subroutine PRESOL for analysis of variable topology, which means calculation of global variable numbers which will be coupled. Arrays produced in this subroutine will facilitate the establishment of the array for specification of prescribed variables and the right-hand side array. After the establishment of element matrices in a user made routine any of the routines for establishment and solution may be called. The direct methods are Crout elimination and factorisation based on element factorisation. If the available size of primary memory is small compared to the space required for the coefficient matrix the Crout solution can be made in steps with use of secondary memory. The iterative method is the conjugate gradient method with different

Interaction problems in soil-structure mechanics with material nonlinearity

Abstract Finite element analysis of soil-structure stress interaction and sand-clay flow interaction is discussed in the paper. The soil may be a one- or two-phase medium, depending on if fully drained, partly drained (consolidation) or undrained condition is considered. Transient behaviour is investigated. Yield hinge theory is adopted for the structural members while visco-plasticity, plasticity or a combination of visco-plasticity and plasticity are adopted for the soil skeleton to account for inviscid yield and creep. Adopted yield criterions are of cone type and according to the Critical State Theory. Finite element calculations for the stability analysis of a natural slope in clay and the interaction of a frame resting on a consolidating elastic-plastic subsoil are presented.