Study of wave shaping techniques of split Hopkinson pressure bar using finite element analysis

Abstract

The split Hopkinson pressure bar (SHPB) continues to be one of the most common methods of testing materials at high rates of strain. Elevated rates of strain, such as those found in impact and explosive applications, have been shown to induce phenomena such as strain hardening and phase transitions that can significantly affect the strength of most materials. Due to its relative simplicity and robustness, the SHPB remains one of the preferred platforms for evaluating mechanical properties of materials at rates of strain approaching 10 4 in/in-s (s -1 ). At the National Institute for Aviation Research (NIAR), research has been conducted to study the wave shaping techniques of SHPB using finite element analysis. The SHPB consists of two long, slender cylindrical bars, denoted input and output bars that "sandwich" a cylindrical test specimen. Utilizing a high-pressure gas gun, a third cylindrical steel bar, known as the striker bar, is fired at the input bar, causing a compressive stress wave to travel through the input bar to the input bar - test specimen interface. At this interface, a portion of the stress wave propagates through the test specimen while the remainder of the pulse reflects back through the input bar as a tensile stress wave.