Characteristics of the stress-strain state and structural changes in axisymmetric samples under sign-alternating deformation by free and constrained bending

The paper presents the results of computer modeling and experimental studies of the parameters of the stress-strain state and structure of the material during deformation by the method of alternating multi-cycle bending of a long-length workpiece (bar, wire rod) around a rotating roller in free and constrained conditions. The material for the study was long-length rods of low alloyed bronze for electrical applications - the Cu-0.5%Cr alloy. It was found that after 4 bending cycles with the workpiece turning through 90 degrees around the longitudinal axis, a gradient field of accumulated strain with maximum values in the peripheral region and minimum in the central region of the workpiece is formed in the workpiece before each subsequent processing cycle. Accordingly, the structural state also has a gradient distribution over the grain size. Constrained bending conditions provide a more uniform deformation field and lower average stresses in the deformation zone, which in turn leads to a smaller structural gradient in the cross section of the sample. After 4 cycles of free bending, a grain-subgrain structure with a minimum grain size of 7.0 +/- 0.5 mu m is formed in the surface layers of the workpiece, while in the central region, the grain size is 45 +/- 5 mu m.