Analysis and Detection of the Pit Formation under Rolling/Sliding Contact Loading

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This study dealt with a problem of surface crack under rolling/sliding contact stress field. In order to discuss the surface crack propagation on the basis of fracture mechanics, stress intensity factors of the surface crack were analyzed exactly and the internal crack shape was detected accurately. The conclusions can be made as follows.(1)The numerical solution of singular integral equations on the basis of the body force method was discussed in the analysis of 3-D surface crack. To obtain the numerical result accurately, the unknown functions of the body force densities which satisfy the boundary conditions were approximated by the products of the fundamental density function and polynomials. Here, the fundamental density function was chosen to express exactly the stress field due to an embedded elliptical crack in an infinite- body. The boundary condition was found to be highly satisfied and very accurate stress intensity factors along the crack front were given by the present method.(2)The Internal shape of an inclined surface crack in a semi-infinte body was detected from data of strains mesured around a region of the crack when the location and the surface length of the crack were already identified. The unknown parameters, the depth and the inclination angle of the surface crack, were determined through the condition which minimizes the squre sum of residuals between measured strain distributions and computed ones for an assumed crack. The strains due to the vertical force applied on the free surface of the cracked body were used as the primary information. The numerical experiment showed that the crack shape was determined with good accuracy from switably chosen two measuring points of the strain.