Experimental Study of Fatigue Crack Overload Retardation in X80 Grade Steel

The tests of fatigue crack overload retardation were performed to gain a some what deeper understanding of overload retardation. We present an experimental investigation of fatigue crack retardation behavior caused by intermediate single peak tensile overload under constant amplitude cyclic loading. The compact tension (CT) specimens of API grade X80 pipeline steel were used in fatigue test. The results show there was an instant crack extension during overloading for the tested overload ratios. As soon as the overload cycle was removed, instant delay in crack growth occurred. The results should be of interest for fracture mechanics prediction models on fatigue crack growth under variable amplitude loading and overloading effect for oil and gas pipelines.