Occupant Response Sensitivity Analyses Using a Lumped Mass Model in Simulation of Car-to-Car Side Impacts 856089

Results of a sensitivity study, based on lumped spring/mass modeling approaches for the characterization of structural and occupant responses in 60° and 90° side impacts, are presented in this paper. Test data from collisions between a moving deformable barrier (MDB) and the side of a Volkswagen Rabbit in two crash configurations, simulating 60° and 90° impacts, are used to derive the force-deflection characteristics of the nonlinear springs in the model.

The mathematical model is used to investigate the sensitivity of occupant responses to parametric changes in the striking and struck car characteristics. The variables included in this parametric study are striking vehicle and struck vehicle stiffnesses, crash configuration, impact velocity, occupant-to-door clearances, and padding characteristics. The striking car and struck car side stiffnesses are varied in the range of ±40 percent and ±30 percent, respectively, from the nominals. The effects of padding material characteristics and padding thicknesses up to 6in are evaluated. The effects of the above parametric changes on predicted thoracic probability of injury using the National Highway Traffic Safety Administration (NHTSA) Thoracic Trauma Index (TTI)(1) are also presented.

The results showed that the rib, spine, and pelvis peak accelerations generally increased with increases in striking vehicle stiffness and impact velocity. Increases in struck car side stiffness and the addition of door padding reduced the peak rib, pelvis, and spine accelerations. The results indicate padding is very effective in reducing the thoracic probability of injury. It is observed that the probability of injury at Abbreviated Injury Scale (AIS) levels of 3 or greater in a 30-year-old male will be reduced from 50 to 20 percent by adding a 3in-thick padding in a 90° collision with the striking car moving at 26mph and the struck car moving at 13mph, respectively. It is also observed that the relative effectiveness of the above changes in vehicle characteristics is a function of impact speed.