Contact Fatigue Analysis of an Elastic-Plastic Layered Medium With a Surface Crack in Sliding Contact With a Fractal Surface

Contact fatigue of a layered medium consisting of an elastic surface layer and three elastic-plastic underlying layers in sliding contact with a rigid and rough surface was analyzed with the finite element method. To include multiscale roughness effects and self-affine surface features, the topography of the rough surface was characterized by scale-invariant fractal geometry. A contact algorithm was used to identify the critical segment of the rough surface to be used in the contact fatigue simulations. The tensile and shear stress intensity factors and the direction and dominant mode of crack growth were determined from the crack-tip stresses. The effect of surface cracking on the evolution of plasticity in the second layer and the significance of topography (fractal) parameters on crack growth are interpreted in terms of the contact pressure, stress intensity factors, and maximum equivalent plastic strain. It is shown that a transition from tensile to shear dominant mode of fatigue crack growth occurs as the crack tip approaches the interface, resulting in further crack growth almost parallel to the layer interface. The obtained results illustrate the important role of surface roughness in contact fatigue of layered media.