Further assessment of deceleration-time histories for occupant injury and the damage of protected object in a crash stop

Crash signal is generally given by a deceleration-time (or a force-time) history measured in a crash stop. Occupant injury and damage of protected object are highly related to the parameters of the crash signal. This paper assesses deceleration-time histories in a crash stop from two aspects, i.e., (i) minimisation of head injury index; (ii) physical modelling using single-degree-of-freedom (SDOF) model. A mathematical description for the determination of the safest deceleration-time history for head injury is presented, and seven well-recognised equivalent crash signals are analysed with constraints of identical velocity change and stop distance. Iso-damage/injury boundaries based on both methods are constructed using non-dimensional quantities. Results show that the preferred deceleration-time history depends on the selection of the injury (or damage) criterion and the ranges of parameters in the crash stop problem. These findings may support the design of cushioning or energy absorbing systems for the crashworthiness of vehicles, air and space crafts, ships and packages.