Author(s)

A de A Motta, E B Becker & N F F Ebecken

Abstract

The class of physical problems of metal structures subject to rapid, large amplitude loads, such as occurs when they are submitted to an explosion blast, involves large deformations and inelastic action. Current state of art in explicit dynamic Finite Element Analysis codes require time steps limited by stability requirements rather than by accuracy. For very high rate processes, accuracy would require a very small time step so that the stability limit does not penalize. Acceptable accuracy may not require such small steps if implicit methods are considered. The implicit methods used in quasi-static analysis, however, require the solution of large systems of equations, and several such systems must be solved at each time step to satisfy the dynamic equilibrium when using Newton iteration. The direct matrix solvers that are used incur in computational costs that grow as n m2, where n is number of degrees-of-freedom and m is the band of the front width, thus resulting in prohibitive costs for very large problems. In this work, the use of higher order, implicit time integration and matrix-free solution of the system of equations is explored, Computational efficiency of explicit codes is combined with the inherent stability of implicit methods.

Keywords