Experimental and numerical studies on pulse shaping techniques used in split Hopkinson pressure bar for testing concrete material

Abstract

Split Hopkinson pressure bar (SHPB) is commonly used to characterize materials under high strain rates. However, conventional SHPB tests on brittle materials has encountered several experimental challenges for the high strain rate loading. In relatively brittle materials like concrete, the deformation of the specimen is very small when subjected to the impact loading; hence, it is very difficult to obtain the prerequisites of valid SHPB tests like dynamic equilibrium and constant strain rate in the specimen. To overcome these issues, the current study presents the importance of the pulse shaper approach in SHPB application for dynamic characterization of concrete material. The pulse shaper serves as a function of increasing the loading duration of the incident pulse. An incident pulse with a longer loading duration is a preferred loading pulse for achieving dynamic stress equilibrium in the specimen. Selection of appropriate dimension of pulse shaper assists in facilitating dynamic stress equilibrium and constant strain rate in the specimen. In the present experimental study, copper pulse shapers are used for evaluation of concrete under high strain rate loading using an SHPB setup. Parameters such as the effect of dimensions (diameter and thickness) of pulse shapers on the loading pulses, dynamic equilibrium, constant strain rate, and material responses are studied. Experimental results revealed the prediction of suitable pulse shapers for 50-200 /sec strain rates. In addition, numerical simulation is also performed, and results are validated with the experimental data.