ИСТИНА

Many structural materials display anisotropic plastic properties of different degree. This anisotropy may be the result of manufacture and forming processes of materials. Along with anisotropy, their behavior may demonstrate the asymmetry in the mechanical properties. The simplest example of this asymmetry is the difference of the stress-strain curves and the yield limits under conditions of tension and compression in the same directions in a material. These effects were experimentally studied for the aluminum alloy D16, which demonstrated the difference between the yield limits and the stress-strain diagrams for different stress states. Generally, the mechanical properties of materials may be expressed as the functions of direction of the applied load and some parameters characterizing the stress state type. The generalized constitutive equations for the characterization of these effects were proposed. The properties of structural materials, which exhibit the dependence on the type of stress state and the direction of the applied loads, are studied. On the base of rigid-plastic media model, a number of solutions of boundary value problems are obtained. The dependence of stress distribution in plastic areas and the values of limit loads on the parameter that characterizes the stress state sensitivity of material’s properties are investigated. The proposed constitutive relations give the possibilities to perform the calculations of limit loads with increased accuracy.