New dummy head prototype: development, validation and injury criteria

Head injuries cause a large proportion of fatalities to road users particul arly motorcyclists. Currently, helmets are assessed using rigid headforms a nd criteria related to acceleration measured at the centre of the headform. This system is not representative of the human head, which comprises a bra in that moves relative to the skull in an impact. Finite element techniques were used in the design, development and validation of a new dummy head pr ototype named Bi-mass 150. It has been constructed using a Hybrid III headf orm and comprises two masses: a skull and a mass to represent the brain att ached to the skull with a damped spring system. The novel feature of this d evice is that it can simulate the brain - skull relative displacement at a frequency close to 150 Hz. This is the frequency recorded in tests in vivo. The prototype was made by removing mass from a Hybrid III dummy head and f ixing to the centre a metallic mass, which simulates the brain. The two com ponents were connected by means of a plastic element such that the natural frequency corresponded to the 150 Hz measured in-vivo. The outputs from thi rteen accident reconstructions, using an instrumented helmeted headform, we re used as inputs to the FE model. The results are the first part of the pr ocess to establish bi-mass related injury criteria, and, in turn, to provid e a much more human-like headform for evaluating and optimising head protec tion systems.