Tooling Effects on Edge Stretchability of AHSS in Mechanical Punching 2019-01-1086
Edge stretchability reduction induced by mechanical punching is a critical issue in the advanced high strength steel applications. In this study, the tooling effects on the trimmed edge damage were evaluated by the specially designed in-plane hole expansion test with the consideration of three punch geometries (flat, conical and rooftop), three cutting clearances (6%, 14%, and 20%) and two materials grades (DP980 and DP1180). Two distinct fracture mechanisms were identified during the hole expansion history for different testing configurations, and the occurrence of each fracture mode depends on the tooling configurations and materials grades. The DIC measurement indicates that the materials are subjected to different deformation modes and the various stress conditions contributed to distinct fracture initiations. Based on the comparison of hole expansion ratios (HER), the rooftop punch produced the mostly damaged hole with lowest HER and edge dominated failure.
Chao Pu, Ken Schmid, Wei Wu, Panagiotis (John) Makrygiannis, Yu-wei Wang