Fatigue crack growth from plain and cold expanded holes in aluminium alloys

Fatigue crack growth iri open holes in aluminium alloys 2024-T351 and 2650 was investigated. Tests were carried out using plates containing plain hole s and cold expanded holes in aluminium. The tests explored the influence of the applied stress, the ratio of the minimum to the maximum applied stress , R, and crack closure. Longer fatigue lives of specimens with cold expande d holes were obtained provided that the applied load ratio was less than 0. 7, and the maximum applied stress was less than 0.5 of the yield strength. The decrease in fatigue crack growth in cold-expanded specimens was related to higher crack opening stresses which is a consequence of the presence of compressive residual stresses arising from cold expansion. Fatigue crack g rowth rates were described as a function of;ln effective stress intensity f actor, which was determined using measured crack opening stress. Measured c rack opening stress was also compared with opening stress determined from f atigue crack growth rates. (C) 2000 Elsevier Science Ltd. ALI rights reserv ed.