A dynamic punch method to quantify the dynamic shear strength of brittle solids

Shear strength is an important material parameter for brittle solids. This parameter has been extensively used in material failure models. Although a few methods have been proposed to quantify this parameter under the static loading condition, there is no such a method available to measure it under dynamic loading conditions. This paper presents a punch shear device to measure the dynamic shear strength of brittle solids. In this method, a split Hopkinson pressure bar system (SHPB) is used to exert the dynamic load to a thin disc sample, which is placed in a specially designed holder to minimize the bending stress induced by punching. The sample holder also allows the punch head to load the sample directly and in combination with momentum-trap technique in SHPB, it enables soft recovery of the rock plug and rock ring produced by the punching test. The flexibility and applicability of this method is demonstrated by the application of an isotropic and fine-grained sandstone. Within the theoretical framework of the classical Mohr-Coulomb failure model, the obtained dynamic shear strengths are consistent with the dynamic tensile strengths for the same rock from the literature.