Effect of high strain rate on plastic flow and frictional behaviours of AA7075-O aluminum alloy

The influence of strain rate on plastic flow and frictional behaviours of AA7075 aluminium alloy, in the O-annealed temper state, was studied. To this purpose, axisymmetric and ring compression tests were carried out using both a servo-hydraulic testing machine and split Hopkinson tension-compression bar in the direct version. The flow curves were investigated in a wide range of strain rate using cylindrical specimens characterised by different slenderness ratios; as far as the ring compression tests are concerned, different strain rates were obtained using hollow cylinders with different values of height, and inner and outer diameters. The axisymmetric compression tests showed an appreciable increase in the flow stress and in the strain rate sensitivity as the results given by high speed tests were compared with those obtained under quasi-static loading condition. The analysis of the results provided by the ring compression tests showed that strain rate affects the variation of the inner ring diameter, irrespective of the height reduction and frictional condition