Microscopic inhomogeneity coupled with macroscopic homogeneity: A localized zone of energy density for fatigue crack growth

Abstract Fatigue failure problem is a typical multi-scale problem that passes at least two different scales of micro-scale to macro-scale. Moreover, the microscopic effects play an important role in a fatigue process. However, the microscopic non-equilibrium and non-homogeneity (NENH) is grossly incompatible with the classical concepts of equilibrium used in mono-scale fracture mechanics. Localized energy density zone (EDZ) is used to describe the fatigue crack growth from a micro-flaw to macro-crack. The term EDZ is used to redeem the formalism of using segmented linearity in previous works. In this way, the segmented local linearity would not be confused with the macroscopic fracture mechanics. The EZD term clears the way for describing micro and macro effects in the same model. Micro and macro effects can thus be included in the S–N curves of LC4 aluminum alloy. Specifically, the scatter of the fatigue test data is shown to be contributed by the material microscopic effects.