Crack initiation in smooth fatigue specimens of austenitic stainless steel in211 light water reactor environments

摘要

The fatigue design curves for structural materials specified in Section III of211u001ethe ASME Boiler and Pressure Vessel Code are based on tests of smooth polished 211u001especimens at room temperature in air. The effects of light water reactor (LWR) 211u001ecoolant environments are not explicitly addressed by the Code design curves; 211u001ehowever, recent test data illustrate the detrimental effects of LWR coolant 211u001eenvironments on the fatigue resistance of austenitic stainless steels (SSs). 211u001eCertain loading and environmental conditions have led to test specimen fatigue 211u001elives that are significantly shorter than those obtained in air. Results of 211u001efatigue tests that examine the influence of reactor environments on crack 211u001einitiation and crack growth of austenitic SSs are presented. Block loading was 211u001eused to mark the fracture surface to determine crack length as a function of 211u001efatigue cycles in water environments, Crack lengths were measured by scanning 211u001eelectron microscopy. The mechanism for decreased fatigue life in LWR environments 211u001eis discussed, and crack growth rates in the smooth fatigue specimens are compared 211u001ewith existing data from studies of crack growth rates.