Numerical Simulation and Spectrum Analysis of Dispersion Effect of Stress Pulse in SHPB Experiment
应力脉冲在SHPB实验中弥散效应的数值模拟与频谱分析

In the background of evaluating the improving effect of pulse shaper on loading waveform, stress pulse dispersion effect of different waveforms was compared and studied based on a split Hopkinson pressure bar (SHPB). Three-dimensional finite element model of the bar was established with the help of software LS-DYNA, and rectangle, triangle and half-sine stress pulse were applied on end of bar. The wave oscillation, peak stress and wave rising time vs. propagation distance were analyzed, a theoretical explanation about this relation was presented by means of spectrum analysis. Results indicate that the triangle stress pulse and half-sine stress pulse show less dispersion effect than rectangle stress pulse in every respect; half-sine stress pulse keeps its characteristics better than triangle stress pulse. So half-sine stress pulse may effectively reduce dispersion effect and improve accuracy of 100-mm-diameter SHPB experiment, and is an appropriate loading waveform for brittle materials such as rocks. Spectrum analysis can effectively explain the stress pulse dispersion phenomenon in SHPB experiment from aspect of theory. This shows that the ideal goal of waveform shaping is half-sine stress pulse with a wider period of time.