Stress uniformity and constant strain rate in SHPB test

The stress uniformity in split Hopkinson pressure bar (SHPB) test is analyzed in detail by using one-dimensional stress wave theory. The influence of related experimental parameters is evaluated. The advantages and disadvantages of some typical loading waveform are discussed. For brittle material testing, the governing equation of input waveform for attaining constant strain-rate loading is given. The strain-rate limitation of SHPB test under certain stress equilibrium condition is analyzed and some new conclusion is given. The method for experimental data analysis of SHPB for better accuracy is also discussed. A qualitative analysis of uniformity and the wanted loading waveform have been done for testing elastic-plastic material made by diagrammatic method. The result indicates that for elastic-plastic material, the strain uniformity should be considered.