Modeling of strain rate effects in automotive impact

Sie sind hier: Homepage > Suche

Modeling of strain rate effects in automotive impact

Simunovic, S. / Nukala, P.K.V.V. / Fekete, J. / Meuleman, D. / Milititsky, M.

This paper deals with the effects of various approaches for modeling of strain rate effects for mild and high strength steels (HSS) on impact simulations. The material modeling is discussed in the context of the finite element method (FEM) modeling of progressive crush of energy absorbing automotive components. The caracteristics of piecewise linear plasticity strain rate dependent material model are analyzed and various submodels for modeling of impact response of steeel structures are investigated. An improvement in predictive capability of the crashworthiness models is linked to development of realistic material models and finite elements with better representation of complex strain and stress states in progressive crushing. Strain rate sensitivity is an important component of the material models and needs to be incorporated in the crashworthiness models. The paper reports on the range of strains and strain rates calculated in the explicit FEM programs that are used for evaluation of constitutive models. Strain rate magnitudes of the order of 10 ³ per s provide a reasonable upper limit for the model. Strain rate magnitudes of the order of 10 ² per s are prevalent for shell element sizes that are of the order of 1 - 2 tube shell thicknesses. The viscoplastic option for material modeling provides more realistically feasible strain rate histories. For modeling details of tube crushing, the FEM mesh discretization should be fine enough, as measured by the strain distribution, angle of shell directors, and resulting curvature, to model the crush fold formation. Once the kinematics are accurately approximated, the material model can be investigated for possible indications of material properties in the range where the experimental coupon tests are difficult to conduct. Current results indicate a close link between the strain rate calculations and element type and discretization, and will be analyzed in more detail in the following publications.