Effects of Sample Geometry Imperfections on the Results of Split Hopkinson Pressure Bar Experiments

The problem of specimen geometry imperfections for ductile materials in the split Hopkinson pressure bar (SHPB) experiments is presented in this paper. Impact of five types of imperfections most frequently encountered in experimental practice and the resulting errors in the position of the specimen in relation to the axis of the bars on the reflected and the transmitted wave profile and on the shape of the stress-strain curve was analysed. The problem was considered based on numerical analyses using a finite element method. It was found that imperfections disturb mainly the beginning and end portions of the reflected and transmitted pulses, which is reflected in the stress-strain curve profile. However, for ductile materials, influence of specimen geometrical imperfections is small, and therefore the SHPB experiments results can be considered reliable from a practical point of view. In the case of all the analysed imperfections, it can be assumed that for imperfection angles α ≤ 0.3°, errors in determination of the stress-strain curves can be omitted.