Adiabatic shear banding under pure shear loading Part I: direct observation of strain localization and energy dissipation measurements

Adiabatic shear banding under pure shear loading was studied in VAR 4340 steel (HRC 40) using a high-speed photography technique. The development of a shear band was directly observed and the strain and strain rate during localization were measured. The stress-strain curve for the shear banded material and estimates of the energy dissipated and the temperature in the shear band were also obtained. It was found that shear localization occurs in two sequential stages over widths of 60 μm and 20 μm, respectively. Significant strength reduction occurs only during the second stage of localization. Strains of 17 and strain rates approaching 1.4×106s−1 were measured in the band. The total energy dissipated per unit area of shear band was of the order of 0.18 MJ/m2; the corresponding temperature elevation was in excess of 1000°C. The information obtained both in this investigation and in the metallographic and fractographic investigation presented in a companion paper provide insight into the mechanisms leading to the development and fracture of a shear band. Such information can be used to develop micromechanical models of adiabatic shear banding.