Development of a Method to Predict the Rupture of Spot Welds in Vehicle Crash Analysis

This paper describes a new method to predict the rupture of spot welds, suitable for vehicle crash simulation. In a crash simulation used for vehicle development process, the calculation is performed assuming that the spot welds in the vehicle do not rupture. However, if some spot welds rupture in test of a prototype vehicle, the simulated deformation and test deformation may not match, resulting in inaccurate estimation of deformation from simulation. Therefore accuracy of predicting the rupture of spot welds is crucial in accurately estimating the deformation and improving reliability of vehicle crash simulation results. The new method to predict the rupture of spot welds which relates axial and shear forces and bending moment of spot weld to stress around nugget has been developed by authors. Based on developed method, the rupture risk of spot welds has been estimated. The new method was applied to estimate the spot weld rupture using three types of specimens. Results of new method were compared with that of “detailed model” which matches closely with test results. Results of new method showed similar deformations observed in “detailed model”. The discrepancy of the rupture force between the new method and “detailed model” was less than 10%. The new method was then applied to a full vehicle frontal offset deformable barrier simulation. The results predicted precise locations of spot weld rupture. Moreover, since this new method uses force and moment data of spot welds obtained from a crash simulation, it does not require any additional modeling or computational time. Therefore the new method is suitable for crash simulation in vehicle development.