THE EFFECT OF ANISOTROPY IN FRACTURE-TOUGHNESS AND YIELD STRENGTH IN THE TEARING OF DUCTILE SHEET MATERIALS

The dependence with orientation of the yield strength and tearing fracture toughness of cold-rolled 64/36 alpha-brass 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.