Fundamentals of Fatigue Crack Initiation and Propagation: Some Thoughts

The prediction of fatigue properties of structural materials is rightly recognized as one of the most important engineering problem. Therefore a basic understanding of the fundamental nature of fatigue crack initiation and growth in metals has long been a major scientific challenge starting with the first dislocation model of fatigue crack growth of Bilby et al. in 1963. For this purpose understanding the process of emission of dislocations from cracks, and determining precise expressions for the size of the plastic zone size, the crack-tip opening displacement and the energy release rate of the cracks are some of the major technical challenges. In this short paper we comment briefly on some of our important recent results obtained theoretically and by in-situ TEM studies and discuss how they may contribute to the understanding of the phenomena