Theoretical Estimation of the Endurance Limit of Metal Materials by the Characteristics of Their Static Strength and Microstructure Based on the Linear-Elastic Fracture Mechanics

A methodology for theoretically estimating the endurance limit of a material for conditions of multicycle fatigue is proposed. The estimation is based on the fact that under these conditions, a nonpropagating surface fatigue crack of one grain size exists at the level of the applied stress range equal to the endurance limit. In this regard, the tools of linear-elastic fracture mechanics were used in the development of the methodology, but with corrections for the size and geometry of a short fatigue crack. The methodology allows for estimating the endurance limit of smooth specimens under symmetric and positive stress ratios of the loading cycle. The initial data for the estimation are the characteristics of the static strength and microstructure of the material. The reliability of the proposed estimation is confirmed by experimental fatigue data for structural alloys of various classes taken from the literature.