B-Model Approach to Fatigue, Fatigue Crack Growth, and Wear for Durability Assessment.

Based upon available data, a detailed statistical analysis has been made of the fatigue crack growth process. Much has been learned about this process including it's history dependence, and the class of acceptable cumulative distribution functions of the time for a crack to increase a specified amount. Two potential probablistic models have been suggested and an initial investigation has been carried out. A methodology has been suggested for adaptive updating of a model of cumulative damage based upon service information to improve the accuracy of maintenance procedures to achieve a prescribed reliability. Based on the data, the effect of increase in length on the fatigue life was investigated. It was found that the weakest link idea was not applicable as a model and an acceptable model was proposed. (Author)