The effect of a single peak overload on fatigue crack propagation behavior of polycarbonate was investigated. The results obtained are summarized as follows:
(1) The amount of crack extension produced by a single peak overload was very large, and the amount of crack extension inside the specimen was about equal to the size of plastic zone at the crack tip produced by a single peak overload under a plane strain condition.
(2) The acceleration factor of crack propagation due to a single peak overload was markedly higher than that in metals.
(3) The maximum retardation of crack propagation was found to occur immediately after a single peak overload at both the surface and the interior of the specimen.
(4) The degree of retardation increased with decreasing baseline stress, and with increasing the ratio of peak to baseline stress.
(5) The crack opening ratio U measured at the specimen surface was almost constant before and after a single peak overload. This fact suggested that the crack closure mechanism could not be applied to the retardation in polycarbonate.
