Channeled local structural transformations in polycrystal surface layers in alternate cyclic bending

The paper presents experimental data on the stage evolution of channeled local structural transformations in the direction of maximum tangential stress in polycrystal surface layers under cyclic loading. At the first loading stage, islands of surface layers are extruded; at the second loading stage, they coagulate into folded structures. The geometric parameters of the folded structures correlate with the stacking fault energy of the material. The obtained results support the concept of physical mesomechanics about a chessboard distribution of tensile and compressive normal stresses at the weakened surface layer - crystalline substrate interface.