Numerical Simulation for Bar Straightness Effect in Split Hopkinson Pressure Bar

Bars alignment in a Split Hopkinson Pressure Bar influences the quality of signal recorded during experiments, and thus affects the data of material properties being measured. There are some parameters directly related to the bars alignment such as their straightness, the impact face parallelism, and the neutral axis offset. This paper presents the study on the effects of non-straightness of an SHPB bar systems, dome shaped specimen, and striker bar to incident bar offset using numerical simulations. The bar component is made of AISI 4340 material with 10 mm diameter and 1000 mm length. The non-straightness of the bars and dome shaped specimen which occured due to the limitation of manufacturing process and availability of material, were measured by using dial gauges with ring supports in every 100 mm. First the simulation of an SHPB using ideal bar geometries were carried out. The simulations were then repeated by incorporating bar straightness, specimen surface, and striker bar to incident bar offset in the numerical model. From the comparisons of the material properties obtained from all simulations, it can be concluded that dome shaped specimen is the most affecting factor to the results of the SHPB measurement..