Impact tensile test and numerical analysis of the dynamic behavior of sandstone ring specimens using a split Hopkinson hollow tensile bar

Abstract

Most rock bodies encountered in underground engineering projects are subject to dynamic tensile conditions. The purpose of this study is to analyze the feasibility of using hollow circular rock samples in a dynamic direct tensile test and assess the specimen’s dynamic tensile mechanical properties. We used 26 hollow ring red sandstone specimens (HRRSSs) with different strain rates (53.86 s⁻¹ to 104.44 s⁻¹ in dynamic direct tensile tests using a Split Hopkinson Hollow Tensile Bar (SHHTB) test system. Five parameters, i.e., the initial elastic modulus, elastoplastic modulus, ideal elastic energy, ideal elastic coefficient, and energy dissipation ratio, were used to identify five stress stages during loading. The parameters were used to analyze the stiffness and energy evolution of the HRRSSs during loading. Numerical methods were utilized to simulate the damage evolution and destruction of the 12 specimens under dynamic tensile loading. The experimental and numerical results showed that the hollow ring structure was reliable and effective in determining the dynamic and direct tensile mechanical properties of rock materials and expanded the upper limit of the strain rate. The direct tensile failure of the HRRSSs with a low strain rate was due to the connection of multiple weak surfaces, whereas that of the HRRSSs with a high strain rate occurred due to a central stress concentration area that consumed a large amount of plastic energy by penetrating a strong surface. The proposed testing method, specimen type, and analytical models can be used to investigate the mechanical properties of rocks using dynamic direct tensile tests.