Element Formulation to Simulate the Localised Plastic Collapse in the Crash Analysis by Multi-body Approach

The paper illustrates the application of the multi-body approach to the analysis of the crashing behaviour of vehicular structures. This type of approach relays on the possibility of describing the bending and axial plastic collapse through the formulation of two specific elements, by which the collapse of the structure can be modelled. The formulation of these two new elements is based on theoretical kinematic models, that lead to an accurate prevision of the moment vs. rotation relationship in the case of the plastic hinge element and of the force vs. displacement in the case of the axial folding element. Two applications are finally shown, one dealing with a typical idealisation of an automotive frontal frame, the other one dealing with the frontal frame of the ERRI railway vehicle. In both the applications a comparison between MB and FEM crash simulation are shown, in terms of deformed shapes of the structure after the collapse and in terms of diagrams, leading to encouraging accordance. The dramatic reduction of the CPU time obtained by the MB approach makes this approach a powerful tool for the initial evaluation of different layout in the early stage of the vehicle design.