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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.

This paper describes that a method has been developed to estimate the range of the scatter of Head Injury Criterion (HIC) values in pedestrian impact tests, which could help to reduce the range of the scatter of HIC values by applying the stochastic method for Finite Element (FE) analysis. A major advantage of this method is that it enables the range of scatter of HIC values to be estimated and to explain the mechanics of the behavior. The test procedure of pedestrian impact allows some tolerances for the resultant conditions of impact such that the distance of actual impact location from the selected point is within 10 mm and the impact velocity is within ±0.7 km/h [1]. A HIC value calculated by impact simulation under a deterministic impact condition with the nominal input data does not necessarily represent the variation of measured data in impactor tests.

This paper describes the development of a fracture finite element (FE) model for laser screw welding (LSW) and validation of the model with experimental results. LSW was developed and introduced to production vehicles by Toyota Motor Corporation in 2013. LSW offers superb advantages such as increased productivity and short pitch welding. Although the authors had previously developed fracture FE models for conventional resistance spot welding (RSW), a fracture model for LSW has not been developed. To develop this fracture model, many comprehensive experiments were conducted. The results revealed that LSW had twice as many variations in fracture modes compared to RSW. Moreover, fracture mode bifurcations were also found to result from differences in clearance between welded plates. In order to analyze LSW fracture phenomena, detailed FE models using fine hexahedral elements were developed.