A kinetic equation for fatigue crack initiation and growth in the very high cycle range based on fractography and nonlinear dynamics

The paper presents an experimental methodology for estimating the very high cycle life of the AMG-6 aluminum alloy subjected to preliminary deformation, using an in-situ method for determining the accumulation of irreversible fatigue damage, based on an analysis of the nonlinear dynamics of free-end vibrations. The specified method allows us to set the kinetics of the accumulation of fatigue damage and to separate the stages of nucleation and growth of a fatigue crack. Based on the data on the surface morphology and established patterns, a kinetic equation is constructed for the nucleation and growth of fatigue cracks in the very high cycle loading range. This equation, based on empirical parameters related to the structure of the material, will allow us to determine the number of cycles for the nucleation of an internal crack and its emergence to the surface.