FRACTURE ANALYSES OF WELDED COMPONENTS

This paper presents a calculation methodology for failure analyses of jointing systems such as weldlines submitted to dynamic crash loading. The numerical analysis of automotive welded component integrity requires to take account of the complex multi-physical phenomena involved during the manufacturing process in order to provide a better understanding of its in-service behaviour. Indeed, weldlines are one of the main jointing element within aluminium structures due to the robust process technology and to good durability and crashworthiness results. The assessment of weldline properties is still a problem, especially in complex crash loading, where weldlines are one of the main items of full car crash behaviour prediction. This is the motivation for an investigation on a methodology combining both welding process and crash simulations. We first present the calculation methodology, based on local/global approach, taking account of the physical phenomena involved during welding, computed locally, to predict the global crack initiation of automotive components and the way it propagates. The theoretical models used for the simulation of the interactions between heat transfer, metallurgy and mechanics as well as the micro-mechanical damage model used for failure are then briefly recalled before describing the way to take into account the metallurgical transformations and the induced plasticity due to welding process during crash calculation. The second part of the paper deals with toughness assessment of aluminium T-joints made of extruded profiles submitted to a bending moment. Two joint configurations are calculated and results are then compared with experiments. This investigation was conducted in the framework of a European project called IMPACT for Improved Failure Prediction for Advanced Crashworthiness of Transportation Vehicles. One of its aims was to set up a method and to improve the software capabilities in order to properly simulate the failure of jointing systems