The Formation of Edge Cracks during Rolling of Metal Sheet

Abstract

Many metals tend to develop edge cracks during hot and cold rolling. Edge cracks need to be removed by a trimming operation, and they may cause rupture of the sheet in the rolling mill. Hence, there is a strong motivation to understand the mechanisms of edge crack formation and to develop predictive tools for controlling the phenomenon. The present work explores the applicability of damage mechanics models to this problem. In conjunction with a plausible failure criterion the Gologanu-Leblond model, which is based on non-spherical ductile void growth, is able to predict edge cracking and the characteristic zigzag damage pattern on the edge of the rolled sheet. The experimental determination of the model parameters remains a challenging task, since the stress and strain history at the edge of a rolled sheet is substantially different from the situation in a tensile test, and also from that in other conventional laboratory tests.

Prediction of damage in cold bulk forming processes

“…Both the Gurson and the Gologanu-Leblond models predict the final fracture in principle, but the prediction is reasonably accurate only for high stress triaxialities, while for low triaxiality, both models are too stable and in fact do not predict fracture at all [8]. Hence, it is necessary to impose failure criteria.…”

“…Hence, it is necessary to impose failure criteria. Following the work by Riedel et al [8] a combination of two criteria is used in this paper; failure occurs as soon as one of these two criteria is fulfilled. Among the two criteria the Thomason criterion [10] usually dominates at high triaxiality.…”

Analysis of Microstructure Effects on Edge Crack of Thin Strip During Cold Rolling

“…[12] The surface and longitudinal cracks have been reported in continuous casting. [13,14] Edge crack evolution during rolling was analyzed, [15][16][17][18] and microstructure influences on crack formation were investigated also. [19,20] Additionally, the influences of the grain size on crack initiation and crack growth were investigated.…”

“…The edge crack will initiate when the void volume fracture reaches a critical value of around 3 pct. An equation for rate of void nucleation [17] is shown as follows,…”

Prediction of Edge Crack in Cold Rolling of Silicon Steel Strip Based on an Extended Gurson–Tvergaard–Needleman Damage Model

“…It is also used to predict plastic damage in cold rolling [1], Recently, Yan et al [9,10] silicon steel strip with precut notch in tandem cold rolling, in which the initiation and propagation of the edge crack is caused by the longitudinal tensile stresses and stress concentration in roll ing gap with the existence of edge notch. In fact, under low stress triaxiality, the governing failure mechanism is characterized by shear localization of plastic strain of the intervoids ligaments due to void rotation and distortion [11], But the GTN damage model cannot capture this damage mechanism which makes the prediction result not that accurate in rolling condition [12], In order to circumvent this limitation, an extended GTN model incorporated with shear damage mechanism in the evolution of damage was proposed by Nahshon and Hutchinson [13]. In fact, under low stress triaxiality, the governing failure mechanism is characterized by shear localization of plastic strain of the intervoids ligaments due to void rotation and distortion [11], But the GTN damage model cannot capture this damage mechanism which makes the prediction result not that accurate in rolling condition [12], In order to circumvent this limitation, an extended GTN model incorporated with shear damage mechanism in the evolution of damage was proposed by Nahshon and Hutchinson [13].…”