Numerical models of plastic zones and associated deformations for a stationary crack in a C(T) specimen loaded at different R-ratios

To understand the nature of cyclic plastic deformation and damage on a fatigue crack tip, in-depth plane strain elasto-plastic finite element analysis was conducted on a compact tension specimen. In the cyclic plastic zone, low cycle fatigue is the dominant cyclic deformation mode during symmetric load cycling, while ratcheting is dominant during asymmetric load cycling. The size of cyclic plastic zone depends upon the amplitude of stress intensity factor while, the size of monotonic plastic zone depends upon the maximum stress intensity factor. The size of monotonic plastic zone is equal to cyclic plastic zone during symmetric load cycling.