Abstract
A detailed fractographic analysis of fatigue crack retardation due to peak overloads was performed on a 2124 T351 aluminum alloy. The influence of an overload ratio K OL /K max equal to 1.3 was investigated for the stress intensity factor ranges corresponding to K OL /K max values of 16.5 and 22 MPa m 1 2 . Microscopic growth rates were measured on compact tension specimens at midthickness (plane strain) and near the edges (pseudoplane stress). The crack retardation after a peak overload was observed to extend over the length of the calculated plane strain plastic zone due to the overload. The crack retardation near the surface of the specimen was greater than in the plane strain region near the center. The models of Wheeler and Willenborg were found to provide a fair approximation of the retardation phenomenon.
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