A Better Way to Crash-Test Rivets

Carmakers are turning to a broader array of materials to reduce vehicle weight. But connecting unlike combinations of steel, aluminum, magnesium and plastic often requires mechanical fasteners such as rivets.

Simulating rivet behavior in a crash has been difficult because stresses vary as the riveted parts deform, notes the Fraunhofer Institute for Mechanics of Materials. in Freiburg, Germany.

Fraunhofer researchers, working with colleagues in Berlin and Paderborn, say they have developed formulae that can reliably forecast performance on a rivet-by-rivet basis under various bending, pulling and sheering loads.

Fraunhofer scientists were joined by colleagues from the Laboratory for Material and Joining technology in Paderborn and the Assoc. for the Advancement of Applied Computer Science in Berlin.

The team subjected 15 combinations of riveted materials to slow and fast bending, pulling, pushing and sheer forces. Then it integrated results with mathematical equations that contain parameters to account for different materials, densities and other factors.

The result is a fully developed simulation tool that can calculate the ability of each rivet to withstand the strains it would experience in a crash. Manufacturers would first simulate a crash to determine what forces appear at which points in the vehicle, then feed that data into the Fraunhofer formulae.