Combined Adhesion and Friction Effects on Cylinder-on-Flat Elastic–Plastic Microcontact

Abstract

Considerable research efforts have been expended in the studies of various types of microcontact devices. One such case is the microelectromechanical switches (MEMS) involving metal-to-metal microcontacts. These microcontacts involve many geometries including cylinder-on-flat interfaces. Further, these microcontacts operate under the combined effects of adhesion and friction and also under the cyclic loading condition, so the understanding of microcontact stress state as well as the induced adhesion force during a load cycle is needed. This study investigates the microcontact interaction between deformable smooth cylindrical segment and deformable smooth flat surface with and without adhesion force and also with and without friction using a finite element methodology. Surface integration method based on the Lennard–Jones potential is used to compute the adhesion force, which involves traction–repulsion interactions outside the contact area of contacting bodies. Effects of several parameters (power exponents of pressure function, energy of adhesion, equilibrium separation distance, contact profile adjustment, and separation distance between interacting bodies) on the adhesion force are analyzed. Influence of adhesion force on the contact area and the stress state of contacting bodies during loading and unloading along with friction effects are investigated. The adhesion force in cylinder-on-flat microcontact decreases with increasing external applied force and with the elastic–plastic material behavior. Contact areas during increasing and decreasing portions of an applied load cycle are not equal at a given load level. Contact area changes non-linearly even when the applied external force varies linearly. Contact area increases in the presence of adhesion force and with the elastic–plastic material behavior. However, the adhesion force decreases while the contact area increases between elastic–plastic bodies in comparison to those between elastic bodies. The maximum stress state is neither at the contact surface nor at the instant of maximum applied external force. The stress state changes considerably in the presence of friction, but contact area does not.