In this study, inclined surface cracks in an elastic orthotropic half-plane exposed to contact loading at the material surface are examined for both open and closed crack assumptions. At first, mixed mode stress intensity factors are computed for fully open crack assumption depending on the solution of singular integral equations, obtained by Full Fourier Transform techniques. Unless fully open crack assumption is valid, the suitable crack closure mode is determined. Both crack tip and full length closure modes are examined. Singular integral equations are solved with a suitable expansion-collocation technique depending on the closure mode. Finally, the closed portions of the cracks, contact pressure distributions between crack faces and modified mode II stress intensity factors are computed considering sliding crack face conditions. The main result of the analyses is the influence of the material parameters, the crack orientation angle and applied load on mixed mode stress intensity factors, closed portions of the cracks and the contact pressure distributions in the closed parts.
This paper presents a multi-layer model for moving contact problems of functionally graded coatings whose physical properties have general spatial variations. The coating is assumed to be composed of an arbitrary number of layers and perfectly bonded to an elastic substrate. Wave equations for the layers and the substrate are derived in accordance with the plane theory of elastodynamics. The equations are solved by the application of Galilean and Fourier transformations. Flat and triangular punch profiles are considered, and the formulation is reduced to a singular integral equation of the second kind in both cases. The integral equations are solved by means of Jacobi expansion and collocation techniques. Proposed procedures are verified through comparisons to the results available for a special case in the literature. Parametric analyses are carried out for functionally graded coatings possessing ceramic-rich, metal-rich, and linear profiles. The results presented demonstrate the influences of factors such as punch speed, coefficient of friction, material property variation profile, and contact-length-to-thickness ratio on contact stresses, punch stress intensity factors, and required contact force. It is shown that the multi-layer model is required to account for general property distributions in a functionally graded coating subject to moving contact.
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