Failure prediction of quenched boron steels in crashworthiness simulation

Helmut Gese



The criteria for passenger safety have been tightened step by step in the last years. This has caused a wide use of quenched boron steels for the passenger cab design, especially for A-pillar and B-pillar. Meanwhile also components with tailored tempering are used to adapt the material properties according to local needs. The introduction of those boron steels has brought some new challenges for the numerical simulation. In the field of crashworthiness simulation a predictive simulation of quenched boron steel components without a comprehensive assessment of material failure – including failure initiated from spot welds - is not possible. The material model MF GenYld+CrachFEM - can be used together with all major explicit finite element codes for crashworthiness simulation via the user material interface - provides comprehensive failure criteria for quenched boron steels. This includes the prediction of localized necking, ductile normal fracture and ductile shear fracture. It is possible to adapt
the material properties locally by a mapping of the hardness provided by the quenching simulation. The material model also provides the possibility to directly model the material failure in the HAZ around spotweld with solids or with a macro model in combination with a shell mesh. The lecture will introduce the material model, discuss the necessary experiments for the parameter identification and will provide simulation examples based on FEA code LS-DYNA.