Effects of Boundary Conditions and Posture on Simulations with Human Body Models of Braking Events

The aim of this study was to investigate the effects of boundary conditions and postures in simulations with human body models (HBMs) when replicating volunteer tests in an occupant environment. Data from sled tests with a peak acceleration of about 0.5 g from male volunteers seated in a backward mounted seat in passenger posture were used for this study. A stepwise approach was taken for the positioning of the HBM by gradually adjusting the original HBM in driver posture to the subject’s posture as target, since this made it possible to specifically study the influence of the posture of certain body regions. The simulations were run with different HBM versions (THUMS V4, THUMS V5, THUMS V6) in passive state (no muscle activation) and with V5 and V6 in active state (relaxed/reactive). The responses from different HBMs were generally consistent. The leg posture showed a comparatively smaller influence than the arm posture. In general, it was observed that more movement between the wrists and the thighs resulted in larger head excursions, suggesting torso support via this loading-path. In addition, the seat model was identified to play a major role on peak head excursion when compared to simplified modelling approaches.