A NEW LOADING TECHNIQUE FOR MEASURING SHEARING PROPERTIES OF MATERIALS UNDER HIGH STRAIN RATES

Impact shearing loading technique at high strain rates is an important foundation for studying of dynamic behaviors and micromechanism of materials. Using the split Hopkinson pressure bar (SHPB) technique, material behaviours can usually be investigated under strain rates up to 104s^-1. To obtain strain rates that exceed 104s^-1 under dynamic shearing, however, pressure-shear plate impact technique or direct impact method with an air-gun launched projectile has to be used. In this paper, a new double-shear specimen that can be used under the SHPB technique is proposed. With this method, dynamic shear properties of materials can be tested precisely under strain rates ranging from 103 to 105s^-1. Complex interfaces or connectors are not needed between the specimen and the bars. With the aid of a simple fixture, the specimen can contact with the bars directly, with its transverse movements limited. In this work, shear stress-shear strain curves of pure copper were acquired at strain rates between 1 400 and 75 000 s^-1. The dynamic loading processes were modeled by ABAQUS/Explicit to check the validity of this testing method. The results show that the shear component dominates the stress and strain fields, which are distributed uniformly in the central part of the shear zone. The measured shear stress-shear strain curves agree very well with the simulation results. It shows that the new double-shear specimen provides a convenient and e ective way to test dynamic shear properties of materials under high strain rates.