The effect of anisotropy in fracture toughness and yield strength in the tearing of ductile sheet materials

Abstract

The dependence with orientation of the yield strength and tearing fracture toughness of cold-rolled α-bass and acetate sheets was determined. Parallel strips were cut into larger sheets of the same materials, rolled up on a slotted key, and converged to form pointed tongues which became detached from the larger sheets. The tongue length: width aspect ratio varied with direction in the plane of the sheet. A rigid-plastic fracture mechanics model of sheet tearing, which explained tear path convergence on the basis of minimum work rate [1] is extended to include ‘lift-off’ of the sheet under the slotted roller and gives agreement between the measured aspect ratios and the variation with direction of the independent determinations of yield strength and toughness.