Abstract
The paper is aimed to the area of simulation and virtual reality in engineering design in the transport safety. The research used the combination of experimental and mathematical methods. The subject of this study was a collision of a pedestrian and a passenger car. Road accident statistics indicate that pedestrians and cyclists are involved in a significant portion of car accidents. Their injuries occur as a result of the contact with a moving vehicle at relatively low speeds. Lower extremities and pelvis sustain injuries in the most frequent cases. The head of a pedestrian is not a frequently injured part of the body, however, according to the statistics head injury is often the reason of the pedestrian death. Therefore head performance and protection is discussed in the paper.
Various studies of pedestrian impact demonstrate existence of several types of injury mechanisms. The most frequent one is described in this work. The front bumper strikes the pedestrian leg in the area of the tibia and the knee. Then the pedestrian thigh or pelvis is struck by the leading edge of bonnet. Then the pedestrian rotates around the leading edge until the arms, head and chest clash into the bonnet or the windshield. The aim of this study is kinematics and dynamics analysis of the movement of a crash test dummy in collision with the impactor representing a compact passenger car. Mathematical modelling was used for a detailed analysis of the collision. The mathematical model was developed in MADYMO environment. Those parts of the vehicle were modelled that are relevant to the pedestrian impact. The parameters of this model were chosen to represent our test vehicle Olcit Club, a compact size hatchback. The model combines multibody and finite element modelling techniques. The mathematical model was validated by comparison with the experimental data obtained from the crash test. Furthermore, the model of the bonnet was validated by comparison with a headform impactor test. The test used the middle class personal car and the available dummy. The test was carried out at velocity 25 km/ h and initial figurine posture was face to vehicle. Velocity of the impactor, acceleration of head and thorax have been recorded during test. The collision history was recorded by high-speed camera as well. The obtained data provides sufficient number of information for preliminary mathematical model validation.
The following modifications of the mathematical model provided some ideas of possible improvements and estimations of the pedestrian load and possible injuries that occurred during a collision. The modified mathematical models were based on the experimentally validated model. Also, one of the reasons of the model modifications was a possibility to equip the model with more sensors than one could have during the physical test. The vehicle model used in the following analysis was also modified to improve the vehicle dynamical behaviour with respect to the test. More sophisticated dummy models were chosen from the Madymo dummy database, because their design is considered to provide a significantly better biofidelity. These models are equipped with a large set of pre-defined output channels, which are needed for measuring the bio-mechanically relevant data. On these models, the influence of the initial vehicle velocity, dummy size and initial posture of the dummy was studied.
Head performance reduction methods ware discussed in the end of the paper. Front end of vehicle could be divided into two zones. The first one was the bonnet and the second was the windshield and the windshield panel. The method of head performance reduction was different for each zone. The zone of bonnet was focused in the paper. Head performance was possible to control, thus reduced by bonnet skin and sub-skin frame layout and material, therefore some modifications of bonnet ware designed. Purpose of designed and discussed modifications was to obtain more pedestrian friendly course of acceleration curve.
Series of additional crash tests will be realize at collaboration with Motor Vehicle Research Institute. The tests at different initial velocity and using different size dummy will be carried out. Results of tests are expected to use for checking out of the sensitivity analyse outcomes.