Ductility of aluminium alloy AA7075 at high strain rates

Under dynamic loading the stabilising effect of increased strain rate sensi tivity of the material restrains neck formation in tension tests and leads to an increase in ductility. On the other hand the adiabatic character of t he deformation process reduces the flow stress and promotes instability, lo calisation and adiabatic shear band initiation. Furthermore, the notch sens itivity of the material increases with increasing strain rate. Dynamic and quasi-static tension and compression tests were carried out on the age hard enable aluminium wrought alloy AA7075. There, dispers distributed precipita tions are often the starting point for ductile fracture caused by impact du e to the nucleation, growth and coalescence of voids and micro-cracks in ca se of tension. Neck formation under tensile loading and instabilities like shear bands in case of compression are discussed on the basis of the theory of imperfections under consideration of the increased strain rate sensitiv ity of the material and the adiabatic character of the deformation process at high strain rates. In case of tensile loading, tests with various notche d geometries allowed the study of the influence of degree of multiaxiality. Through combination of experiment and simulation, the influence of strain rate on the local fracture strain could be determined for tensile and compr ession loading.