Achieving synchronous compression-shear loading on SHPB using helical structures

Abstract

The mechanical response of materials under dynamic combined compression-shear loading is critical for many engineering applications. This study proposes a technique that utilizes a helical structure to convert axial compression waves into coupled compression–shear waves, thereby achieving synchronized dynamic loading in a conventional Split Hopkinson Pressure Bar (SHPB). A predictive formula was derived from stress wave theory to determine the shear-to-compressive stress ratio in the transmission bar. Finite element simulations were conducted to investigate the influence of key geometric parameters of the helical structure on the stress conversion. The results indicate that the number of helical rods has a negligible influence, whereas the lead angle and interfacial friction significantly affect the amplitudes of the transmitted stresses. Experimental validation demonstrated strong consistency with both theoretical predictions and numerical simulations, confirming the reliability of the proposed model. The developed technique offers precise control of loading synchronization and stress ratios, while maintaining the advantages of simplicity, reusability, and low cost. Furthermore, the dynamic mechanical behavior of 1060 Al was characterized, validating the effectiveness of the proposed experimental method.