AN INVESTIGATION-OF THE CRACK TIP DEFORMATION CHARACTERISTICS OF SLOWLY GROWING FATIGUE CRACKS

摘要

The technique of selected area electron channeling has been quantified and used to map the shape and quantitative strain distribution within the plastic zones attending fatigue crack tips in 304 stainless steel, 6061-T6 aluminum, and Fe-3Si steel. Simultaneously, crack tip operning displacement, the mechanisms of yielding and decohesion, and maximum shear strains have been measured using high magnification SEM of replicas. Overload plastic zones and their relation to fatigue crack retardation have been characterized. Observed values of all of these parameters have been compared with predictions of various analytical models.