ANALYSIS OF CROSS AND VERTICAL BUCKLING IN SHEET-METAL ROLLING

In sheet metal rolling, shape defects called ''cross buckling'' or ''v ertical buckling'' sometimes appear, which are wrinkles like washboard s. The direction of the crest line of the cross buckling inclines at a certain degree against the rolling direction, while that of the verti cal buckling is parallel to the rolling direction. In this study, anal ysis of the cross and vertical buckling is performed using the element ary theory of buckling. First, we calculate the stress distribution in three-dimensional sheet metal rolling near the exit cross section ins ide the roll gap. Next, we calculate the residual stress distribution near the exit cross section outside the roll gap. Furthermore, sheet m etal buckling is analysed using the residual stress distribution. Type of buckling, distance between neighboring wrinkles, inclination of th e crest line of the wrinkles against the width direction and the regio n where the wrinkles appear are obtained. We compare analytical result s with published experimental results, and find that the former agree well with the latter. Hence, we conclude that this method of analysis is valid, and that the cause of the cross and vertical buckling is the residual stress distribution near the exit cross section outside the roll gap. (C) 1998 Elsevier Science Ltd. All rights reserved.