The formation of adiabatic shear bands in copper during torsion at high strain rates

Abstract

The formation of adiabatic shear bands, which are narrow deformation bands with intense strains, in copper at high strain rates has long been questioned due to ductility of copper and its ability to exhibit uniform deformation at relatively large strains. However, in some instances when copper is tested in torsion at shear strain in excess of 103 s−1, it has been reported to develop adiabatic shear bands. This study examines the occurrence of adiabatic shear bands in torsion specimens of commercial pure copper (99.94% Cu) as a function of the initial torque and angle of twist. Adiabatic shear bands (ASBs) were observed using scanning electron microscopy. It is concluded that a mesomechanical property such as adiabatic shear bands can be induced in ductile materials such as polycrystalline copper. The source of these bands is correlated to the extensive shear deformation before fracture.