Modeling of Spot Weld under Impact Loading and Its Effect on Crash Simulation

Spot weld is the primary joining method to assemble the automotive body structure. In any crash events some separation of spot-welds can be expected. However, if this happens in critical areas of the vehicle it can potentially affect the integrity of the structure. It will be beneficial to identify such issues through CAE simulation before prototypes are built and tested. This paper reports a spot weld modeling methodology to characterize spot weld separation and its application in full vehicle crash simulation. A generalized two-node spring element with 6 DOF at each node is used to model the spot weld. Separation of spot welds is modeled using three alternative rupture criteria defined in terms of peak force, displacement and energy. Component level crash tests are conducted using VIA sled at various impact speeds to determine mean crush load and identify possible separation of welds. The component tests are then simulated using finite element models where the proposed spot weld modeling methodology is used. Comparison of simulation results with tests confirms that the proposed spot weld modeling methodology is reasonable in capturing spot weld behavior and predicting potential separation in crash simulation. It is found that the energy-based criterion is more suitable for predicting the weld separation in crash simulation.