Description of the effect of AlMg6 alloy strength decrease during temperature increase under dynamic loading

The work is devoted to a theoretical and experimental study of mechanisms related to plastic strain localization under dynamic loading. A mathematical model that takes into account structural relaxation and thermal softening is built within the framework of the study on the basis of wide-range constitutive equations. The proposed model is capable to adequately describe the deformation of plastic materials (metals and alloys) in the range of strain rates of 102-104 s-1 and in the temperature range from 0 to 0.7 of the melting point. AMg6 aluminum alloy was chosen as a material under study as it is a promising material for mechanical engineering. However, all the obtained results can be applied to a wide class of materials: metals and alloys. The model parameters were identified using experimental data (stress-strain diagrams) at various strain rates and temperatures. The series of original experiments on punching disc-shaped barriers by a cylindrical projectile was carried out to test the constructed model. During the experiment, the impact velocity and the temperature on the back surface of the barrier were measured at the moment of an intense localization of plastic deformation and fracture. The strain rate in the experiment ranged from 500 to 30,000 s-1. As a result of the numerical studies, it was shown that defects play a critical part in during strain localization for AlMg6 alloy at strain rates of less than 104 s-1. Thermal softening begins to make a significant contribution at strain rates above 104 s-1. This theoretical result is also confirmed by the original experiments on the penetration of barriers.