Studies of shear band velocity using spatially and temporally resolved measurements of strain during quasistatic compression of a bulk metallic glass

We have made measurements of the temporal and spatial features of the evolution of strain during the serrated flow of Pd40Ni40P20 bulk metallic glass tested under quasistatic, room temperature, uniaxial compression. Strain and load data were acquired at rates of up to 400 kHz using strain gages affixed to all four sides of the specimen and a piezoelectric load cell located near the specimen. Calculation of the displacement rate requires an assumption about the nature of the shear displacement. If one assumes that the entire shear plane displaces simultaneously, the displacement rate is approximately 0.002 m s–1. If instead one assumes that the displacement occurs as a localized propagating front, the velocity of the front is approximately 2.8 m s−1. In either case, the velocity is orders of magnitude less than the shear wave speed (∼2000 m s−1). The significance of these measurements for estimates of heating in shear bands is discussed.