This paper presents original physical and numerical human head models followed by their modal and temporal validation against human head vibration analysis in vivo and cadaver impact tests. The human head FE model developed by ULP presents two particularities: one at the brain-skull interface level where fluid-structure interaction is taken into account, the other at the skull modelling level by integrating the bone fracture simulation. Validation shows that the model correlated well with a number of experimental cadaver tests and predicted intracranial pressure accurately. However, for long duration impacts the model reaches its limits. The skull stiffness and fracture force were very accurately predicted when compared with values from the literature. In a second step a new dummy head prototype named Bimass is presented. It has been constructed using a Hybrid III headform and comprises two masses: a skull and a mass to represent the brain attached to the skull with a damped spring system. The displacement at a frequency close to 150 Hz as recorded under vibration analysis in vivo. Helmet damage from thirteen motorcycle accidents was replicated in drop tests conducted in collaboration with Transport Research Laboratory (UK). Simulation of these accidents using both FE model and Bimass dummy head led to the first tentative proposals for tolerance limits and injury criteria relative to specific injury mechanisms. (Author/publisher).
Abstract