A model of edge cracking in sheared and bent steel plate

Abstract

Steel plate subjected to transverse force bending will develop cracks in the outer edges of the curved portion of the bent part, if bending strains are sufficiently high, and the plate has been cut to size by shearing. A pilot study was undertaken to determine the feasibility of a model for predicting the approximate lengths of such cracks. It was stipulated that the model be sufficiently compact to be programmed on a hand-held programmable calculator. A semi-empirical model was developed based on the hypothesis that edge cracks propagate away from the edge and into the plate until the effective strain based on the sums of the true shearing and bending strain components equals the effective plane strain fracture strain.

The model was applied to three different steels. Variables were blade gap and blade sharpness in shearing, and rolling direction in bending. Bending conditions were kept constant with the plates bent in plane strain and with the punch radius equal to the plate thickness. The tests showed that the model predicts the range of edge crack lengths for the chosen shearing and bending conditions with reasonable accuracy.