Simplified modelling of vehicle frontal crashworthiness using a modal approach

The paper presents a simplified method to analyze the crashworthiness of vehicles. This is especially aimed at guiding designs in the early stages when a decision has to be made from a fairly large number of ideas. The object of the method is to drastically reduce the size of the finite element model and the C.P.U computing time, while preserving a sufficient degree of accuracy for an efficient selection between different designs. With this purpose in mind, beam elements are used to model structural components that absorb most of the crash energy. All non-linearities (plasticity, breakable attachments and intermittent contacts (shocks) are concentrated in plastic hinges and nonlinear contact spring elements, respectively. Rigid parts (engine block, gear box etc.) are modelled as rigid solids. Furthermore, computation of the dynamic response of the vehicle is performed by using a substructuring method, based on modal synthesis. The method was successfully applied in analyzing several crash tests carried out on real vehicles and in performing various parametric studies of industrial interest. A case study of a car crashing into a barrier with an overlap of 40% is presented listing those results of most interest to designers.