Outils de conception au choc : un panorama

Abstract

The increase in the number of individual and collective means of transport leads to a potential raise in the amount of dangerous collisions for the human beings. Following this remark, and also due to government pressure, the automobile industry has since the 1970s conducted extensive research in the aim of reducing these risks and if necessary to limit the effects by improving passenger safety. To reach these objectives, two main actions have been driven through the development of preventive and palliative technologies, namely, active and passive safety. Even if these advances have led to considerable improvement, the actual situation remains worrying, so that this particular set of problems still represents a major challenge to our society. In terms of passive safety, two different important phenomena are in competition with each other; on the one hand, energy dissipation must be maximised, whereas on the other hand, deceleration levels sustained by the passengers must be minimised. A compromise must therefore be reached so as to make a good crashworthiness design. To meet these objectives, two main methods of calculation strategies are put forward, which are the global and local strategy studies. The global strategy method can be solved by using elementary approaches. The goal is to bring solutions to problems encountered in complex structural modelisation (or structural assemblies) by reproducing only the global phenomena. The main interest of this approach is to study rapidly the dimensionning and optimisation of the structure. Multibody articulated systems and beam modelisation coupled to upper bound methods are particularly adapted to this problem. The local strategy study which is meant to reproduce as accurately as possible the behaviour of structures to choc, uses the finite element method. This method allows one to tackle and to solve with the help of powerful computers the problems which have up to now been left without solutions. Nevertheless, the mesh which corresponds to the back bone of finite element analysis still demands considerable time during the structural modelisation process. This unfortunately does not permit using this approach in an iterative dimensionning process during a planning stage. Furthermore, even if geometric non-linearities have been well implemented in nowadays calculation codes, a lack of information on material non-linearities is present due to a poor knowledge of dynamic material behaviour. This article tends to give an overview on these various methods as well as their industrial applications.