Simulation models of side impact are used to improve understanding of the dynamic events which can only partially be observed and measured in full scale impact tests, and to explore the effects of modifying structural design without the expense of building and impacting large numbers of experimental vehicles. It has also been suggested that they could be used for legislative testing. Simulation models for frontal impact into a rigid block were first developed about fifteen years ago. Subsequently side impact models were developed along similar lines, to represent impact by a rigid impactor, in accord with the then current methods of full scale testing. The car structure was represented by a small number of discrete masses, connected by (non-linear) springs and dampers. The dummy occupant was initially represented by a single rigid mass. When a deformable barrier front was first used to replace the rigid barrier, this was merely represented by an additional spring in the model, and an attempt was made to introduce a more representative model of the dummy thorax. Comparison with full scale test results has shown that this was an oversimplification and that relative motion between different parts of the car structure, and between different parts of the dummy, is an important factor in determining the likely level of injury. Currently work is proceeding on developing more realistic lumped parameter models which can reproduce these effects, and which can take some account of the effect of dynamic impact (compared with quasi-static loading)on the spring elements. In many ways the ideal solution would be to use a dynamic finite element model, but these are complicated to set up, and very expensive in computer running time. An exciting possibility for the future is the development of hybrid models, in which critical elements can be modelled by finite elements, but in which the bulk of the model still consists of lumped parameter elements.
Samenvatting