Surface construction for orthrotropic perfectly elastic-plastic Murnaghan material

The problem of constructing a yield surface is described. The magnitude of the stress velocity potential is explained graphically. The parameters of an elastic-plastic process are introduced: a modified R. Schmidt parameter and an analogue of the Lode parameter, the sign of which changes only when the singular point of the plasticity curve passes. The formal work area of the Murnaghan law is calculated, the real area will be much smaller. An effect similar to the Bauschinger effect for the deviator of the stress tensor is assumed to be fair. In the basic experiments of uniaxial and biaxial tension, compression and shear, a piecewise-linear generator with vertices at the corresponding singular points of the plasticity curves is determined. The magnitude of the effect is approximated by a quadratic dependence in the place parameter and piecewise-linear one in the hardening parameter. According to the magnitude of the effect, at the point of the active process there is a singular point of the curve, into which the basic generator moves. The yield surface is constructed by ductility curves drawn through the generator. Determination of the magnitude of the effect under repeated loading after unloading is considered.