Inertia Effects in High-Rate Compression Experiments of Soft Materials

Abstract

Inertia effects in Kolsky compression bar experiments have long been studied ever since the establishment of this high-rate characterization technique. As the materials under investigation become softer, new uncertainties arise in relation to the inertia stress induced by acceleration of specimen radial deformation rate. When the soft specimen is compressed at constant axial strain rate, the radial deformation rate gradually ramps up as the volume of the material needs to be conserved. This acceleration introduces an extra radial pressure term which superimposes on the intrinsic material response. In this study, we presented some recent experimental evidences on how this pressure affected the radial deformation behavior of annular soft specimens under dynamic compression at large strains. By incorporating high-speed photography to a modified Kolsky compression bar setup, the radial expansion of several soft rubbers was investigated. Inhomogeneous deformation was identified as the inner boundaries of several annular specimens exhibited counter-intuitive motions.