A FEM code for cyclic plastic deformation which can consider the effect of lattice rotation and rate-dependency is developed. Using this code, the non-uniform deformation behavior of f.c.c. single crystal is investigated under cyclic loading condition. Results of the analyses are summarized as follows, 1) Although it is assumed that the strain hardening of slip systems depends only on the back stress of each slip system, the deformation modes under tensile and compressive loading are different. 2) Even if the strain amplitude is only 3.5x10-3, the localization of plastic strain becomes more obviously as loading cycle proceeds, and the irreversible slip occurs in the region where plastic strain concentrates. It can be assumed that this phenomena is related to the mechanisms of PSBs and intrusion generation. Introduction The microscopic view of the damage accumulation process (initiation of micro-crack) during cyclic loading can be summarized as follows:
appearance of local plastic strain,
localization of these plastic strains and then generation of irreversible slip,
formation of persistent slip band (PSBs),
accumulation of irreversible slip within PSBs,
formation of intrusion within PSBs,
growth of intrusion and then formation of a micro-crack.
Therefor, in order to improve a prediction method of crack initiation and failure life, it is needed to acquire the knowledge about the microscopic mechanisms of plastic strain localization and irreversible slip generation. Crystalline FEM analysis is applicable to investigate such mechanisms. In the previous report, Tomita et al.(1997), the authors have proposed two microscopic hardening rules which can be used for cyclic deformation analysis. It has been shown that the distribution of local stress and local plastic strain are quite non-uniform. However, we could not simulate the generation of irreversible slip and the acceleration of local plastic strain localization for lack of the lattice rotation effect of crystals.
