Multiple Fatigue Crack Growth Prediction Using Standard Stress Intensity Factor Solutions

Abstract

It is generally believed that multiple fatigue crack growth prediction is difficult with the use of standard stress intensity factor (SIF) solution calculations because of the complicated nature of such issues as magnification and shielding effects. Therefore, almost all the existing FFS rules such as the ASME Section XI Code and JSME Code adopt the procedure whereby multiple cracks grow independently after applying a certain alignment rule based on the initial crack configuration and are combined immediately into an enveloping crack when the crack tips touch. In some cases, the results of the procedures in the existing FFS rules can be unrealistic and may lead to unreliable predictions of the service life of cracked components. This paper describes a new approach to predicting multiple nonaligned fatigue crack growth life by the use of standard SIF solutions. Several examples, as compared with numerical analysis by the body force method for two-dimensional models and experimental results in the literature for three-dimensional models, illustrate the accuracy and effectiveness of the procedure.