Introduction of a 1000 MPa crush tip within a Usibor® 1500-AS axial crush rail using in-die heated hot stamping

Axial crush is an important mechanism used in automotive front end structures to absorb impact energy. In this work, numerical simulation is used to investigate the crush response of a Usibor® 1500-AS axial crush rail with tailored properties achieved using in-die heated (IDH) hot stamping. In this case, the targeted properties in the softened zone correspond to a tensile strength of 1000 MPa. A finite element model is utilized to predict the crash performance of the tailored in-die heated 1000 MPa crush tip within a Usibor® 1500-AS rail. A numerical parametric study is presented, comparing the crush response based on fracture loci determined using two different plane-strain strain experiments, one the plane-strain Nakazima dome test and the other the VDA-238 V-bending test. In addition a number of different mesh regularization treatments are considered. The predictions exhibit a strong dependency of the onset of fracture upon the plane strain fracture strain level and degree of mesh regularization.