Ductile-brittle Transition Behavior of Structural Steel in Fatigue Crack Growth under Low Temperature

Abstract

The effects of specimen geometry, specimen thickness, stress ratio and frequency on the fatigue crack growth rate of structural steels were examined at 123 K to clarify the formation mechanism of a cleavage during fatigue crack growth, and the condition of the final fracture. Fatigue crack growth rate at 123 K was found to be sensitive to the stress ratio, and to be considerably increased by the occurrence of a cleavage during striation formation. The value of Kci at which the first cleavage appears was about 20 MPa√m regardless of specimen configuration of the material caused by cyclic straining ahead of the crack tip. The value of Kfc at which final fracture occurs is fond to increase as the specimen thickness does not satisfy the size requirement for small scale yielding.