Optimal design of rear-seat restraint system based on new safety seat during frontal collisions

Abstract

Owing to the narrow rear-row space of compact cars, the head of a rear-seat occupant can easily hit against the headrest or the seatback of the front seat in frontal collisions, thereby causing injuries to the occupant. A prototype design of a new safety seat is proposed to increase the safety of rear-seat occupants. The aim of this study is to investigate the protective effects of the new safety seat and further optimise the rear-seat restraint system in 100% and 40% overlapped frontal collisions. First, a simulation model of the restraint system is developed and validated. Second, the effects of the original seat and the new safety seats with different torsional stiffness of the torsion spring on the injuries to a female rear-seat occupant are compared. Finally, the design parameters of the rear-seat restraint system are optimised globally to minimise injuries to the female rear-seat occupant. Compared with the original seat case, the head injury criterion HIC15 and thorax 3 ms resultant acceleration T3MS of the female rear-seat occupant in the new safety seat case reduce, whereas the neck injury criterion N_ij increases. When the torsional stiffness of the torsion spring decreases gradually, HIC15 and T3MS decrease. The optimum torsional stiffness of the torsion spring determined via analysis is 10 N m/°. The optimal combination of the design parameters of the rear-seat restraint system is obtained. After optimisation, for the 100% overlapped collision, HIC15 and T3MS decrease by 40.20% and 5.75%, respectively, N_ij decreases by 35.94% and the peak left and right femur forces (F_L and F_R, respectively) decrease by 9.65% and 12.26%, respectively. For the 40% overlapped collision, HIC15 and T3MS reduce by 39.92% and 11.64%, respectively, and N_ij, F_L and F_R decrease by 8.89%, 7.50% and 6.09%, respectively.