Characterization, modelling and simulation of deformation and fracture behaviour of the light-weight wrought alloys under high strain rate loading

Abstract

The flow behaviour and ductility of the Aluminium alloy AA7075, Magnesium alloy AZ80, and Titanium alloy Ti–6Al–4V are investigated in quasistatic and dynamic uniaxial compression and tension tests at nominal strain rates range of 0.001 s - 1 ⩽ ε ˙ ⩽ 5000 s - 1 and temperatures between 20 and 450 °C. Shear tests using hat-shaped specimens are carried out by quasistatic and dynamic loading at shear rates ranging between 0.01 s - 1 and 120 000 s - 1 and at a temperature of 20 °C. Using experimentally determined stress–strain curves, the effects of strain (strain hardening), strain rate (strain rate sensitivity) and temperature (thermal softening) on the stress and the deformation at fracture are determined, showing that both flow stress and limits of possible deformation are controlled by strain rate and temperature. Metallographic investigations give an explanation about formation and evolution of damage in the deformed material. The material flow behaviour of the tested alloys under high strain rates loading is described with a constitutive material law with assumption of domination of damping controlled glide processes, by taking the adiabatic behaviour of the deformation process into consideration. Compression, tension, and shear tests are simulated by the finite element method in order to validate the constitutive material law used. The numerical modelling of tensile tests on differently notched bars has allowed the determination of the failure criterion for AZ80 and Ti–6Al–4V under quasistatic and dynamic tensile loading.