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A possible mechanism of the crack growth is described by calculating stress intensity factors for a semicircular surface crack under a spherical Hertzian contact moving over a cracked elastic half-space surface. In the analysis the crack is assumed to be inclined at an angle of 45 deg from the surface. In particular, the effects of surface traction, frictional force between crack faces, and oil hydraulic pressure caused by oil penetrated into the crack are discussed.
Kaneta et al. (Sun,) studied this question.