A round-robin analysis was conducted which evaluated and compared different methods currently in practice for predicting crack growth under random loading. This report describes the prediction method used by the Fracture Mechanics Engineering Section (FMES) at NASA-Langley Research Center. It also presents the ratios of the predicted lives to the test lives for eleven of the thirteen specimens tested.

Fatigue crack growth under stationary Gaussian random loading is considered. A specially developed computerized testing system and software are used for generation of the random loading and investigation of crack growth. The sliding summation numerical method was used for generation of a random loading history characterized by a given autocorrelation function. As far as the loading history of a sufficient length is generated a sequence of maxima and minima is extracted and arranged with the predetermined frequency. The next Operation is elimination of the small amplitude cycles in accordance with the predetermined threshold value and. determination of the minima and maxima two-dimensional distribution of the edited process. A specially built transition matrix derived from this distribution was used for the real-time generation of the random loading during the test. Experimental investigation of the developed random loading generation procedure and crack growth process was performed using aluminium alloy multicrack panel type specimens providing possibility of observation of an array of simultaneously growing cracks. Dependence of fatigue crack life time on random loading parameters as well as stochastic characteristics of crack growth were studied. (MM).

This book demonstrates fatigue crack growth under random loading graphically. This state-of-the-art monograph introduces an expert system for crack growth predictions, particularly based on crack closure. The system is developed after years of research by the authors by using the Math-type software consisting of 5 parts. This system is unique as it is fundamentally different from previous systems as it focuses on fatigue crack growth predictions based on fatigue crack closure. This book can be a useful guide for practicing engineers, researchers, and students in the fields of mechanical, aerospace, or civil engineering.