Probabilistic Defect Size Analysis Using Fatigue and Cyclic Crack Growth Rate Data

TL;DRAbstract

The fatigue failure mechanism of many cast metals and high-strength alloys involves initiation and propagation of a crack from an initial defect to a critical size where fatigue failure occurs. Crack growth rate and fatigue data can be combined to estimate the initial size of the defect that led to failure. This technique has been developed and used to provide statistical interpretations of fatigue data and to determine the probabilistic size distribution of critical defects and the specimen size dependence of the average critical defect size. An expression for the fatigue curve that incorporates the initial defect size (ai) is produced by integrating an analytical expression for the cyclic crack growth rate curve that includes a threshold stress intensity factor. For two different values of ai, two fatigue curves are generated that can represent scatter in fatigue data from two specimens of the same size or average fatigue curves for specimens with two different sizes. This scatter or

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