Effects of abrasive wear and chipping-type abrasive wear on degradation of edge stretchability with advanced high-strength steels

Abstract

This paper proposes a new strategy for inducing wear on a trim die to examine the degradation of edge stretchability with advanced high-strength steels. To independently examine trim die wear, the wear is categorized into abrasive wear and chipping-type abrasive wear. Geometric changes in fixed and moving trim dies were precisely examined every 2500 cycles of a repetitive trimming test lasting up to 15,000 cycles. A uniform wear shape could be generated after 5000 cycles; thus, it was possible to extrapolate the blanking cycles by controlling the die clearances, as well as realistically simulate chipping wear by micromachining the chipping shapes onto a worn trim die. The degradation rates of the edge fracture strain of DP980 and TRIP1180 were compared for various combinations of trimming die sets, which exhibited significantly different tendencies even though they had similar levels of initial edge stretchability. TRIP1180 had a high degradation rate of 35% for the edge stretchability after fewer than 15,000 cycles. In contrast, a degradation rate of 11% was observed when the DP980 sheet was applied, but the edge stretchability was highly sensitive to chipping-type abrasive wear.