Dynamic load on the head during rear impact against a headrest

A model of the dynamics of a vehicle collision with an energy-absorbing barrier was built in the PC-Crash 10.0 environment, using the following models: vehicle motion dynamics, collision, and multibody models of people seated on seats.The energy-absorbing barrier was composed of connected elements whose motion was described by Newton's and Euler's equations.Rear-seat passengers were modeled as polyhedral systems, each consisting of 20 rigid solids connected by spherical joints.The simulations investigated the effects of different headrest and seatback settings configurations on the dynamic loads acting on the head of a passenger seated in the rear bench seat.The results showed that the value of the coefficient describing the risk of head injury decreased as the backrest tilt angle increased, indicating that the head is better protected with greater tilt.The stiffness of the headrest significantly affected the value of the coefficient describing the risk of head injury, i.e., with a higher stiffness of 20,000 N/m, a strong negative correlation was observed, indicating a lower risk of injury.However, further increases in stiffness may negatively impact the risk of head injuries.In contrast, at lower stiffnesses, the correlation was more variable, with different results depending on the angle of the backrest.The results underscore that proper configuration of the backrest, seat tilt angles, and headrest stiffness are key to minimizing head injuries.Particularly favorable values of the coefficient describing the risk of head injury were achieved at angles of 5 headrest tilt angle and 10 headrest tilt angle and corresponding values of headrest stiffness.In general, a negative correlation was observed between the backrest tilt angle and the HIC 36ms value, i.e., the larger the tilt angle, the lower the HIC 36ms value, which means better protection.At the lower stiffness of the headrest, 15,000 N/m, the correlation was variable, both positive and negative, depending on the backrest tilt angle.