Achieving synchronous compression-shear loading on SHPB by utilizing mechanical metamaterial

Materials in service often experience complex stress states, such as a combination of shear and compression or tension. Therefore, it is crucial to experimentally measure the mechanical responses of materials under complex stress states before designing structures, as these responses differ from those under uniaxial loading. However, conducting combined loading experiments, especially under dynamic impact, is challenging and usually requires complex and costly equipment. In the present work, by employing compression-torsion coupling metamaterials, an easy method is proposed for the first time to achieve synchronous dynamic compression-shear loading on 1D Split Hopkinson Pression Bar (SHPB), which is also feasible for quasi-static experiments on universal material testing machine. The compression-torsion coupling metamaterial can convert a compression wave into combined waves of compression and torsion, and ensures the two waves naturally synchronously act on the thin-walled cylinder specimen. Since the compression-shear dynamic loading experiment can be performed on a traditional 1-D SHPB, it is a cost-effective, convenient, and easily implementable method. Both the dynamic and quasi-static mechanical properties of 1060 Al were measured under various shear-compression ratios, and a well von-Mises yield surface was obtained with strain rate insensitivity, confirming the validity of the proposed experimental methods.