Experimental study of adiabatic shear band propagation in impacted plates

The present work is focussed on experimental study of the impact shearing, and particularly on the propagation of adiabatic shear bands and fracture. The purpose of this paper is to present an experimental setup which has been specially designed at LPMM-Metz to generate propagation of ASB in a rectangular plate specimen. The concept of the force measurement which loads the specimen is based on the elastic wave propagation theory. A flat projectile is launched from an air gun, and it impacts one side of a flat specimen. The impact occurs on the specimen side in between two narrow notches, so that the plastic deformation is localized at the tips of the notches. Those tips are the site of initiation of adiabatic shearing and next propagation of shear fracture. The longitudinal impact force is measured via strain gages cemented on the Hopkinson tube as a function of time. This arrangement permits to estimate the mean velocity of the shear fracturing. In addition, a fast CCD camera is a part of the setup. Several microscopic observations of the cross sections of the fracture zones have been completed using SEM technique. It was found that the experimental arrangement is quite efficient and can provide fundamental data on the kinetics of shear propagation in materials loaded by impact.