Fatigue Failure at Atomic Level

We have seen in Section 17.1 that the basis of the crack origination is the deformation process. The foundation of the fatigue crack propagation is the rapture of interatomic bonding. 

The fatigue crack originates at the surface, then the crack embryo begins to grow. In my opinion, a movement of vacancies to the tip of the crack plays a dominant role in crack growth. 

One would expect a sufficient time to be available for vacancy diffusion even at room temperature since fatigue involves a sufficiently long period of time for crack initiation and propagation. 

An equilibrium concentration of vacancies in the crystal lattice is given by 

The relative number of vacancies which are formed at the intersection of dislocations Cin for face-centered crystals is given by [81] 

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