Bull-bars are often added to many Australian vehicles to minimise damage and maximise the possibility of vehicle driveability after a frontal impact. The increased use of SRS air bags in vehicles has meant that the problem of possible premature air bag deployment during a sub-critical impact speed must be addressed. Finite element modelling (FEM) was used to evaluate the crash "transparency" of several bull-bars fitted to Australian passenger vehicles. Some calibration of the models using static load tests was also carried out. The FEM was used to analyse the action of impact loads using force-time functions developed on the basis of typical vehicle response histories obtained from crash testing of vehicles. The results from the FEM indicated that the bull-bar had very little effect on the crash characteristics of the vehicle. Failure in the bull-bar system typically occurred in the order of mounting plates, attachment bolts and finally the bull-bar itself. This meant that very little energy was absorbed before the bar met the front of the vehicle. The bull-bar system could be designed to obtain a predetermined failure mechanism which would control the impact attenuation properties of the bull-bar system. (A)
Samenvatting