Ductile fracture of Mg–3Al–1Zn alloy under dynamic loads

The evaluation of the physical and mechanical properties of materials at high strain rates plays a key role in improving the accuracy of predicting the stress-strain state of structures operating under extreme conditions. This paper presents the results of a comprehensive experimental and numerical study of the mechanical response of thin-sheet rolled products of Mg-3Al-1Zn alloy (MA2-1) to dynamic punching and uniaxial tension. Magnesium alloy samples were exposed to uniaxial tension at rates ranging from 0.1 to 1000 s-1 and punching with a semispherical indenter at velocities of 10, 5, 1, and 0.1 m/s. A numerical simulation of the experimental conditions was carried out to estimate the resistance to high-speed plastic deformation under uniaxial and biaxial tension and to determine the stress distribution in the Mg-3Al-1Zn alloy plate under the specified loading conditions. To describe the deformation, damage, and fracture of Mg-3Al-1Zn alloy, the computational model was based on the model of the mechanical behavior of the alloy with a hexagonal close-packed (HCP) crystal lattice and the model of damage initiation and growth. The simulation results confirmed that the fracture of the magnesium alloy was ductile under high-speed biaxial tension. It was found that cracks were formed during biaxial tension under conditions of punching by a hemispherical indenter at velocities from 10 to 0.1 m/s at lower values of equivalent plastic strains than during uniaxial tension at similar strain rates. The crack shapes and plate deflections obtained in the calculations of dynamic punching of the Mg-3Al-1Zn alloy plates using the model of damaged HCP materials were consistent with those observed in the experiments.