Analysis of Tool Wear for Trimming of DP980 Sheet Metal Blanks

In recent years, implementation of dual phase (DP) Advanced High Strength Steels (AHSS) and Ultra High Strength Steels (UHSS) is increasing in automotive components due to their superior structural performance and vehicle weight reduction capabilities. However, these materials are often sensitive to trimmed edge cracking if stretching along sheared edge occurs in such processes as stretch flanging. Tool wear is another major issue in the trimming of UHSS because of higher contact pressures at the interface between cutting tools and sheet metal blank caused by UHSS’s higher flow stresses and the presence of a hard martensitic in the microstructure. The objective of the present paper is to discuss the methodology of analyzing die wear for trimming operations of UHSS components and illustrate it with some examples of tool wear analysis for trimming 1.5mm thick DP980 steel. The results of die wear of D2 cutting inserts will be reported based upon measurements of the surface of the die and measuring of the burr height of the samples. Strong correlation between local chipping of the trim die and the local burr height of the trimmed sample will be discussed in the paper. This correlation serves as a guidance that die wear of the cutting edges of the trim die can be monitored off line by observing the shape of the trimmed edges.