2012 年 7 巻 4 号 p. 449-462
Skull fractures occurring under various impacts are required to be evaluated during forensic investigations or during design of a head protection device. Finite element analysis using a human head model is an effective evaluation tool for it, because investigating of the behavior of skull fracture such as the start and the progress can be easily performed. JARI Head Tolerance Curve (JHTC), which is an existing criterion for skull fracture based on the cadaver head drop tests, uses head acceleration as the parameter, though the fractures are mainly caused by stress concentration on local area. In this study, we tried to develop stress-based criteria for skull fracture, and to simulate skull fracture by using a head finite element model, which we previously developed. Forehead dropping simulations with five different conditions were performed, and the results were found to be nearly equivalent to the JHTC tests in terms of effective acceleration of head and its duration time. We then determined critical stresses for skull fracture as a function of duration time, based on the time histories of stresses on the skull surface in the five simulation results. Furthermore, we applied our criteria to two forehead impact simulations. We could observe fracture on the skull followed by sharply decreasing in stress on fractured elements as well as increasing in stress on its neighboring elements, and also variation in shapes and ranges of fractured element distribution. These results indicate that the criteria could evaluate skull fracture in detail under different patterns of impact.
