Character of strengthening of an initially orthotropic material when subjected to simple and complex loadings. Communication 1

Abstract

We have carried out an experimental study of the inelastic properties of solids with simple and complex loadings, producing pure shear strains and the subsequent imposition of strain states of pure shear. 1. The data from experiments with biaxial tension on a specimen of the zirconium alloy E-110 demonstrate the presence of initial anisotropy of the elastic deformation and strength properties. 2. The test specimens have three orthogonal planes of elastic symmetry of the material, directed respectively along the axis of the specimen, along the tangential direction to the cylinder generatrix, and along the radial direction. These are the principal axes. The elastic constants were determined in the direction of these axes. 3. We have pointed out a trajectory of preliminary simple and complex loading that leads to an increase of strength and deformation properties of the material in one of the principal directions of the stress tensor, in comparison with the analogous properties in the case of simple loading. Such a trajectory consists of loading accompanied by partial unloading in one of the directions of preliminary plastic deformation, interruption of the increase of plastic strains in this direction, and an excess of the magnitude of the second principal stress over the first. 4. Regardless of the prehistory of simple and complex loading of the initially orthotropic material, accompanied by partial unloading in the direction of the preliminary plastic deformation, a repeated simple loading σz=2σϕ, equivalent to the action of pure shear with the imposition of hydrostatic pressure, leads to a change in the deformation properties, i.e., to isotropic strengthening of the material. The onset of plasticity in such a repeated simple loading is determined by the stress intensity at the end of the first section of the preliminary loading trajectory, and the point at which this onset occurs is independent of the magnitude of the second principal stress and the intensity of stresses at the end of the second section of complex loading of the preliminary loading trajectory. This indicates that the onset and development of plastic strains along specific slip areasT is determined solely by the magnitude of the maximum tangential stress, and is independent of plastic slips along the other areasT12 orT23.