Quasi-static Polycrystalline Uniaxial Stress Experiments

Abstract

In the range of strain rates from 1 sec−1 to the highest diffraction grating measured value of 70,000 sec−1, inertial contributions are sufficiently important so that the non-linear wave propagation effects of Chapter II must be considered. Strain rates of 1 sec−1 and below are in the domain of quasi-static, uniaxial stress experiments where this inertial contribution is negligible. For these experiments one need only establish that a uniform distribution of stress and finite strain is maintained with only the axial principal stress being non-zero. As will be shown below from the study of over 250 polycrystalline quasi-static, uniaxial stress experiments in nineteen crystalline elements and two binary combinations, the dynamic generalization of Eq. (2.20) is still applicable. As long as strain is increasing at the finite amplitude wave front in dynamic experiments, the integral value of the large deformation mode index r has been found to be stable until the maximum strain is reached. In quasi-static experiments, on the other hand, transitions from one parabolic large deformation mode to another are found to occur as the strain increases.