Cyclic plastic deformation response at fatigue crack tips

To determine the nature of damage acting on a fatigue crack-tip, it is mandatory to know the detailed cyclic plastic deformation response. In this work, cyclic plastic deformation response has been studied on a stationary CT specimen crack-tip in an elasto-plastic finite element frame work at selected R-ratios and ΔK. Chaboche kinematic hardening model has been used to describe material behavior. Monotonic and cyclic/reverse plastic zone identified during plane strain finite element analysis. It is noticed that progressive accumulation of permanent strain i.e. ratcheting occurs in the cyclic plastic zone ahead of a fatigue crack-tip.

► Butterfly type monotonic plastic zone at the ahead of fatigue crack-tip.
► Size of the monotonic plastic zone is higher than the reverse plastic zone.
► Progressive ratcheting behavior has been observed in the cyclic plastic zone.
► Ratcheting strain accumulation increases with the increase in R ratio and ΔK value.