Analytical and numerical contact analyses of semi-infinite media with patterned and rough surfaces

Contact analyses of semi-infinite media with patterned and rough surfaces were performed in order to examine the effects of surface patterning, frictional heating, and surface cracking on the resulting deformation and stresses in the media. Stress and plastic strain results for layered media possessing meandered and sinusoidal surface patterns were compared with those of a layered medium with a smooth (flat) surface and identical layer thickness and material properties subjected to the same normal and tangential loading. Two- and three-dimensional finite element results for the contact stress and deformation fields were obtained for patterned media in terms of coefficient of friction, spherical indenter radius, and sliding repetitions. In addition, a fully coupled thermomechanical finite element analysis was carried out to obtain solutions for the surface temperature distribution and to elucidate the effect of the Peclet number on the maximum temperature rise and subsurface plasticity.; In addition to the studies involving smooth surfaces, a plane-strain model was developed for a layered medium in contact with a rough surface characterized by fractal geometry. A constitutive relation between the mean contact pressure and a representative strain was obtained based on finite element results for a rigid cylindrical asperity in normal contact with an elastic layered medium. The real contact area was obtained as a function of mechanical properties, layer thickness, truncated half-contact width, and asperity radius. These relations were incorporated into a numerical algorithm to determine the contact pressure profiles and stress state based on the distribution of asperity microcontacts. Numerical results revealed that crack initiation is more likely to occur at both the surface and the interface in the case of a stiff layer, while they are more likely to occur at the surface in the case of a compliant layer.; The main findings in this dissertation provide insight into the significance of surface patterning, overcoat properties, frictional heating, and surface cracking on the mechanical and thermomechanical behavior of half-space media with patterned and rough surfaces. The obtained results advance the current state in contact mechanics of thin-film mechanical systems with contact interfaces, such as microelectromechanical devices and hard disk drives, and enhance the understanding about the underlying reasons leading to mechanical failure of contacting surfaces and layered media. (Abstract shortened by UMI.)...