Research on the Influence of Punching Parameters and Selection of Fracture Damage Model for Punching

Abstract

Due to the advantages of high efficiency, low energy consumption and wide applicability, die punching has been widely used in the shearing process of automotive parts. However, it is seldom used on ultra-high strength steel due to the high punching force and risk of tool wear. In this paper, study of die punching process for hot stamped steel Usibor 1500P has been carried out. Firstly, the influence of process parameters including punching velocity, die clearance, punch corner radius, sheet thickness, punch diameter and punch shape have been studied through a specifically designed punching tool. Corner radius at the punch edge can significantly improve the sheared edge quality, and tapered flat-bottomed punch and conical shaped punch evidently reduce and raise the maximum punching force respectively. Secondly, based on the damage thresholds obtained from "iterative prediction-correction" method, finite element fracture model for the die punching process of Usibor 1500P has been constructed and validated, the Oyane and MMC damage models are considered as the most suitable for describing the fracture characteristics of the Usibor 1500P during punching.