Simulation of two-gauge measurement method on the SHPB for testing soft materials

For soft and biological samples, strains tend to be large before any measurable stress is observed, especially compared to materials such as metals or ceramics. This means that for a Split-Hopkinson Pressure bar (SHPB), the loading pulse must have sufficient duration to produce a significant stress-strain response. In addition, the low impedance of soft materials means the transmitted stress tends to be low especially in the initial stages of the experiment. This combination favours the use of longer stress pulses to study soft materials. We outline a method of modifying an existing SHPB system to produce longer, analysable stress pulses. The two-gauge measurement method implements two gauges stations onto a conventional SHPB. Here the theoretical background of this method is presented. A computational approach is then presented and its application to a finite element model simulation demonstrates that the method and the codes are consistent with the desired outcome, of allowing longer stress histories for a modified conventional SHPB. The method can effectively increase the loading duration by up to maximum of ∼200%.