A mathematical model is presented which simulates in 2 dimensions the motion of a restrained car occupant and thereby takes into account the deformations in lumped parameter form which are experienced by the human body as a result of belt loading during a crash event. The human body model has 10 degrees of freedom. In order to allow for a detailed analysis of restraint system performance, independent simplified models of the body regions contacted by a safety belt and of the restraint system itself were developed and combined with the body model. Model validation is performed by comparing the computer calculations with the results of a 50 km/h barrier crash test with sled and dummy.
In view of the pronounced deformation rate dependence of the human mechanical chest characteristics the presently used belt material with its structural damping behaviour, i.e. strain rate independent loading and unloading characteristics, does not seem to offer optimal protection. It is shown that an improved performance within the framework of the mathematical model can be obtained with a restraint system which exhibits a strong viscous, i.e. strain rate dependent mechanical component because such a system would have some capability of adapting its stiffness over a wide range of crash conditions and occupant characteristics.