Calculations of the Meniscus Force and the Contact Force Formed in the Microcontacts of a Rough Surface and a Smooth, Rigid Surface with a Thin Water Film

Abstract

ABSTRACTA present model is developed to calculate the adhesion meniscus force due to a rough surface with surface asperity in contact with a smooth, rigid flat covered by a thin water film. The original thickness of this film before surface contacts is dependent upon the relative humidity in the air. Microcontact deformations of surface asperities in the elastic, elastoplastic, and fully plastic regimes are included in the present model under a normal load. The new water film thickness under the condition of microcontact deformations is considered changing with the normal load, and it is obtained from the equation developed on the basis of the volume conservation principle for the new film thickness and the water film volume displaced by the asperities heights dipping in the film. The meniscus profile is also calculated from the balance of the surface tension force and the pressure difference force across the meniscus profile if the new film thickness is available. Water film thickness and the meniscus force are increased by decreasing the mean separation of two contact surfaces, or increasing the relative humidity, or increasing the plastic index. A significant difference in the meniscus force is found between the present model and the model of the literature, which is enhanced by either decreasing the mean separation, or raising the plasticity index, or increasing the relative humidity. The effects of the meniscus force on the load capacity are also evaluated at different mean separations, relative humidity and plasticity indices.