Evaluation of fatigue crack growth characteristic under the residual stress by cold expansion

Many mechanical fastened methods have been proposed in order to retard crack initiation and to improve fatigue life. In order to the crack which occurs under the cold expansion residual stress, it necessary the stress intensity factor analysis required. From this analysis, it is possible to estimate the stability of fracture mechanical behavior and fatigue life of the fastened structures. The fatigue crack growth tests were performed for the CT(Compact Tension) specimen in which the residual stress by cold expansion had been generated. The cold expansion method delays the crack initiation, but hasten the crack growth propagating from the hole. The crack growth rate increases due to the increase in the cold expansion ratio. da/dN-ΔK curves are slightly different corresponding to the cold expansion ratio, but the curves are included within an agreeable band