Abstract
Retardation of fatigue crack propagation due to a single tensile overload and crack closure behavior were investigated on a high tensile strength steel, HT-80 and an aluminum alloy, A 5083-O by using the unloading elastic compliance method.
Although the delayed retardation was observed at the specimen surface where the plane stress condition dominated, retardation of fatigue crack propagation was found to occur immediately after a peak overload at the interior of the specimen where the plane strain condition was developed. In the latter case, the crack tip blunting due to a overload, which might be the reason of the nodelayed retardation, was confirmed by fractography and also by the load-displacement hysteresis curve. Moreover it was found that the retardation behavior of fatigue cracks which initiated and propagated from the root of the blunted crack could not be explained only by the change of the macroscopically measured crack tip opening level.
