PROJECTS

SiRiCrash

Due to the high ecological pressure and the simultaneously increasing demands on vehicle safety, car manufacturers are increasingly relying on the use of modern high-strength sheet materials.

One disadvantage of these materials is their low ductility, which leads to greater localization of stresses and strain at critical points in the body under crash load and encourages the formation and propagation of cracks. Reliable simulation methods are required to assess whether these cracks are tolerable in terms of occupant protection or whether design changes need to be made. In this project, an alternative approach for the improved simulation of crack propagation by continuous element elimination is pursued.

In contrast to the damage mechanics models mentioned above, this approach is based on fracture mechanics concepts. The problem of discretization error is circumvented by evaluating the stresses and strains in a suitable environment of the critical element, in which the stresses and strains are only slightly influenced by the discretization error (non-local approach). These “non-local” stresses are then assessed using a so-called “Failure Assessment Diagram” (FAD), which was derived in advance for the sheet metal material using experiments and detailed simulations of cracked specimens. If the FAD predicts crack growth, the critical element is deleted and the next leading element before the crack tip is assessed in the same way.

Focus of SiRiCrash

  • development and prototype implementation of this method,
  • derivation of FADs for two selected sheet metal materials (combination of  Mode I and Mode III)
  • possibility of reducing (expensive) fracture mechanics tests to derive the FADs through the increased use of “virtual testing” on the basis of FE detail models is also being investigated.