Analysis of strain paths of sheared edges during hole expansion tests

One of the limitations to the widespread use of advanced high strength steel (AHSS) sheets is the cracking of sheared edges during subsequent stretching operations, as nearly all stamped parts are sheared prior to sheet forming. Cracking at the edge occurs at levels below the conventional forming limit criteria. Understanding the strain path of the sheared edge during a hole expansion test should provide insight into the strain path of a sheared edge when it is stretched during production. As a result, experimental as well as finite element simulations are used for analyzing the strain path behavior of a sheared edge during hole expansion tests. The shearing process changes the global behavior in the sheet during a hole expansion, and the finite element results indicate that the strain paths for points near the edge of the hole during expansion are non-linear due to the presence of the shear affected zone (SAZ). These results are consistent with previously measured experimental values for the strain path.