IMPROVED SPOTWELD SIMULATION WITH LS-DYNA - NUMERICAL SIMULATION AND COMPARISON TO EXPERIMENTS

Functioning of the body of a car structure with respect to stiffness, durability and crashworthiness is mainly dependent on the connection between the manufactured parts, in particular, if mainly shell type structural parts are used. Spot welding is the dominant technique used nowadays to connect shell type parts. Though spot welding is a fully automated process and a well known technique since many years, there is little knowledge about the behavior of the spotweld connections under single strong impulse loading. This knowledge, however, is one major ingredient for a proper repre-sentation in FE crashworthiness models. In order to capture the correct mechanical behavior of a spotweld connection with its complex stress state, in prin-ciple a fully 3D continuum mechanical model is needed, e.g. as the welding process itself has a major influence on the material properties in the vicinity of the spotweld due to the high temperatures involved locally. In addition from experiments it is known that the failure process of a spotweld connection is strongly dependent on the form of the spotweld and local rupture takes place. In FE crashworthiness models, however, such detailed models cannot be incorpora-ted for the many thousands of spotweld connections due to efficiency reasons. Thus alternative models have to be developed to include the major effects of the spotweld behavior within full car crash models with only little influence on the efficiency of the FE analysis. Taking the experiences gained from many years of modeling in the automotive in-dustry a number of different FE spotweld models are discussed and the results of the analyses with LS-DYNA are compared to some experimental results from the investi-gations initiated by the FAT- working group 27 (Forschungsvereinigung Automo-biltechnik e.V. AK 27). Within the analysis particular focus is on the sensitivity of the results concerning the various spotweld models tested on single spotwelds. Finally the influence of the vari-ous models on the results for a realistic part under crashworthiness loading is shown.