An Evidence of Melting along Adiabatic Shear Band in High-Speed Shearing Process.

Abstract

Commercial quarter-hard pure aluminum (Al-1/4H) sheets of 10 mm thickness are tested. A circular disk is sheared from a circular specimen concentrically. Clearance between punch and die is 1 and 0.5%. Two testing machines are used, one of which is aided by a drop hammer for high punch speed (10 m/s) and the other, driven by hydraulic pressure for low punch speed (0.1 mm/s). At high-speed shearing, not only the occurrence of the adiabatic shear band (ASB) but also melting along it is clearly demonstrated by measuring the micro-Vicker's hardness distribution over the sheared-off surface, by optical microscopy of the sheared section, which shows a thin layer with a different microstructure from the adjacent smooth shear flow region, by the mirrorlike appearance of the sheared-off surface, and above all, by a theoretical analysis of the shearing process.