Reserves of strength in plastic deformation. Report 2

The results are presented of experimental and theoretical investigation of transformation of the frontal portion of the loading surface for four series of repeated loadings after a preliminary one complex in trajectory, the first section of which was axial tension and the second orthogonal loading in the plane of main stresses. In three series, repeated radial loadings were made after three types of unloading, complete unloading along a straight line, complete unloading along the trajectory of preliminary loading, and partial unloading along the second section of this trajectory to different values of the parameter of the form of stressed state. In the fourth series, return movement along the section to the point of the break in the loading trajectory and subsequent repeated loadings along straight lines were used. It was shown that the form of the loading surface is substantially determined by the form of the stressed state at the initial moment of repeated loading, the direction of this loading, and the history of unloading. An analysis of the form of the loading surfaces constructed in different series is given and their difference is explained from viewpoints of the theory of plasticity of anisotropically hardening media based on the shear mechanism of deformation.