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A method is presented for predicting the stress corrosion crack initiation (environment-induced crack initiation) resistance of notched components from the results of smooth (unnotched) specimen tests. The predictive procedure is based on the maximum principal surface strain failure criterion and uses Neuber's rule to estimate notch root strains. It is capable of handling elastic-plastic notch stress-strain behavior. The method is shown to be accurate in predicting the results of tests on two notched geometries, representing very different stress gradients, and a number of notch radii corresponding to a wide range of stress concentration factors. A material-environment system was employed in which hydrogen-induced cracking occurs, specifically a 1194 MPa (173 ksi) yield strength NiCrMoV steel exposed to 345 kPa (50 psig) hydrogen sulfide gas. Some additional data pertaining to the definition of crack initiation and the effect of constraint were generated and discussed in terms of their effect on the accuracy of the prediction procedure. The results of the work indicate that the stress corrosion crack initiation resistance of structures and machine parts which contain stress raisers can be predicted by laboratory tests with specimens of much simpler geometries.
prediction, stress corrosion crack initiation, notches, nickel-chromium-molybdenum-vanadium steel, hydrogen sulfide, geometry effects, Neuber's rule, fracture mechanics
Senior engineer, Westinghouse Research and Development Center, Pittsburgh, Pa.