Quantitative Model of the Surface Relief Formation in Cyclic Straining

The cyclic strain localization in crystalline materials subjected to cyclic loading results in specific dislocation arrangement in persistent slip bands consisting of alternating dislocation rich and dislocation poor volumes. In the present model the interaction of mobile dislocations in persistent slip band leading to the formation of point defects during cyclic straining is considered. Point defects are steadily produced and simultaneously annihilated due to localized cyclic straining. The non-equilibrium point defects migrate to the matrix and result in transfer of matter between persistent slip band and the matrix and formation of the internal stresses both in the persistent slip band and in the matrix. Plastic relaxation of internal stresses leads to the formation of the characteristic surface relief in the form of persistent slip markings (extrusions and intrusions). Process of point defect migration is quantitatively described and the form of extrusion and parallel intrusions is predicted under some simplifying assumptions. The predictions of the model are discussed and predicted surface relief is compared with selected observations of surface relief produced by cyclic straining.