Relating fracture mechanics and fatigue lifetime prediction

This article presents how to link together the results of fatigue crack growth tests, analytic fracture mechanics and experimental methods of fatigue lifetime predictions. The study at the beginning investigates the effect of mechanical load redistribution among failed and intact micro-structural bonds along fatigue crack growth to final crack at vulnerable locations in materials and structures under cyclic loads. The microstructural load redistribution model is analytically formulated as a mechanical interaction between fatigue crack growth and fatigue endurance on the macroscopic level. The article in continuation investigates how to link the parameters of fatigue crack growth in fracture mechanics to parameters of fatigue life directly from the work done on crack growth determined by testing. The article at the end illustrates the application of the analytic procedure for fatigue lifetime prediction that combines fracture mechanics and the load redistribution model for determination of S-N curve parameters important in structural analysis and design. In this research the fatigue life time parameters are derived from a single fatigue crack growth experiment instead from normally required sets of fatigue tests for different loading conditions.