A Novel Apparatus and Methodology to Characterise the High-Rate Behaviour of Materials Under Complex Loading Conditions

More advanced testing methodologies and measurement techniques to identify complex deformation and failure at high strain rates have drawn increasing attention in recent years. This study presents a novel combined tension-torsion split Hopkinson bar (TTHB) system that is conceived to generate a combination of tensile and torsional waves in a single loading case and to measure material data representative of real case impact scenarios. Energy-release mechanism is employed to generate both longitudinal and shear waves practically via the quick release of a bespoke clamp assembly. The synchronisation of the longitudinal and torsional waves, and the wave rise time, were experimentally assessed. Thin-walled tube specimens made of two metallic materials were utilised to examine the capability of the developed TTHB system. Four-ligament tension-torsion specimens were also used and the results compared to those obtained using the thin-walled tubular specimens. The capability of the apparatus is demonstrated by the measurement of the failure envelope of standard and additively manufactured materials at high strain rates..