Doctor of Philosophy, The Ohio State University, 2008, Mechanical Engineering

Adhesion, friction/stiction and wear are among the main issues in magnetic storage devices, microelectromechanical systems (MEMS/NEMS), and other commercial devices having contacting interfaces with normal or tangential motion. Relevant parameters, i.e., layer thicknesses and their mechanical properties for the contact solid surfaces, the roles of meniscus and viscous forces for separation of surfaces from liquid films, need to be studied to provide a fundamental understanding of the phenomenon and the physics of the experienced problems. The simulation of contact mechanics and the modeling of separation of two surfaces with and without liquid mediated contacts are effective ways to investigate these issues. In the simulation of contact mechanics, a numerical three-dimensional (3D) rough multilayered contact model is developed to investigate the effects of roughness, stiffness, hardness, layer thicknesses, load, coefficient of friction, and meniscus contribution of elastic-perfectly plastic solid surfaces. The model is based on a variational principle in which the contact pressure distributions are those that minimize the total complementary potential energy. The quasi-Newton method is used to find the minimum. The influence coefficients of the displacements and stresses for a multilayered contact model are determined using the Papkovich-Neuber potentials with a Fast Fourier Transform (FFT) based scheme. Contact analysis of multilayered structures under both dry and wet conditions with and without sliding which simulates the actual contact situations of those devices is performed to identify and obtain optimum design parameters including materials with desired mechanical properties, layer thicknesses, and to predict and analyze the contact behavior of devices in operation. In the modeling of separation of two surfaces with liquid mediated contacts, numerical models of normal and tangential separation of smooth or rough surfaces are developed. The analyses for both (open full item for complete abstract)

Committee: Bharat Bhushan (Advisor) Subjects: Engineering; Mechanical Engineering; Mechanics