EXPERIMENTAL-STUDY OF FATIGUE CRACK INITIATION AND GROWTH FROM COLDWORKED HOLES

The behavior of specimens with holes that were coldworked by radial expansion was studied. The initiation and growth of fatigue cracks was observed for a remote cyclic loading that generated stresses at the hole edge slightly above the yield stress. Coldworking affected the growth rate, not the initiation. Strains near the hole were measured with the moiré technique and used to predict the initiation of cracks in the noncoldworked specimens with reasonable accuracy. Stress intensity factors computed with a linear elastic superposition procedure compared favorably with those measured by crack growth and displacement techniques for cracks longer than 1 mm. © 1979.