Fatigue Crack Tip Plasticity

Abstract
Theoretical calculation and experimental measurement of fatigue crack tip plastic zone size are reviewed, and recent plastic zone measurements using selected area electron channeling are presented. The relationships between state of stress, measurement technique, and plastic zone shape and size are discussed. It is shown that there exists only limited agreement between theory and experimental measurements, but that general conclusions concerning the appropriate plastic zone dimensions for various conditions can be drawn. The importance of plastic zone shape is demonstrated for the case of overload-induced crack growth retardation.