The effect of variable amplitude loading on a 533-B steel in high-temperature air and reactor water environments

This paper describes the efforts to develop an analytical model for the prediction of fatigue crack growth under service-simulated loading typical of power reactor loadings. Experimentally, the program has involved development of a data base of constant amplitude crack growth rate data and a data base of crack extension data for tests conducted with simple overloads and underloads. The final experimental phase was to conduct a series of service simulation tests using the spectrum proposed by the International Cyclic Crack Growth Rate Group. In concert with this experimental work, an analytical model was developed, incorporating capabilities for modeling the load acceleration and retardation effects which were experimentally observed. The development stages of this model are described. The results of the application of this model to the service simulation tests are extremely encouraging. Suggestions to assist in the continued improvement and verification of the model are presented