Female car users are reported to have a higher incidence of soft tissue neck injuries in low speed rear-end collisions than males, and they apparently take longer to recover. This paper addresses the whiplash problem by developing a biomechanical FEM (Finite Element Method) model of the 50th and the 5th percentile female cervical spines, based on the earlier published male model created at the Nottingham Trent University. This model relies on grafting a detailed biomechanical model of the neck and head onto a standard HYBRID III dummy model. The overall philosophy of the investigation was to see if females responded essentially as scaled down males from the perspective of rear end collisions. It was found that detailed responses varied significantly with gender and it became clear that females cannot be modelled as scaled-down males, thus confirming the need for separate male and female biomechanical models and a revision of car test programmes and regulations which are currently based on the average male. Further investigation is needed to quantify the gender differences and then recommendations can be made for changes to the design of car seats and head restraints in order to reduce the risk of soft tissue injury to women.
A biomechanical finite element (FE) model of the 50th percentile male human cervical spine, capable of predicting ligament loadings in whiplash scenarios, has been developed and previously reported. The study reported here analyses the influence of seat back rake on ligament injury in two scenarios: firstly, the in position, where the car occupant is looking forward and the head remains in the sagittal plane, and, secondly, the out of position, where the car occupant is initially looking slightly to one side. In both cases the results show an increase in ligament loading with a decrease of seat back rotational stiffness, substantiating the need for dynamic seat testing. Moreover, comparing individual ligament loading data shows that the initial head rotation scenario is more damaging to the cervical spine than the sagittal plane scenario, confirming a published hypothesis.
A novel approach to obtaining localized bearing contact of spiroid gear drives has been developed. The localized contact is achieved by modifying the pinion tooth surface. With this approach, only the pinion cutter’s geometrical angles and mounting position need to be adjusted, and, hence, it is simpler and more economical than other methods. In this paper the following are presented: overview of the approach, equations for modified spiroid gear tooth geometry, and computer simulation results. The results confirm that the proposed modification of the tooth geometry pennits localized bearing contact.
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