Modeling Sliding Contact of Rough Surfaces with Molecularly Thin Lubricants

Abstract

The sliding contact between two rough surfaces in the presence of a molecularly thin lubricant layer is investigated. Under very high shear rates, the lubricant is treated as a semi-solid layer with normal and lateral sheardependent stiffness components obtained from experimental data. The adhesive force in the presence of lubricant is also adapted from the Sub-boundary lubrication model and improved to account for variation in surface energy with penetration into the lubricant layer. A model is then proposed, based on the Improved sub-boundary lubrication model, which accounts for lubricant contact and adhesion and its validity is discussed. The model is in good agreement with published experimental measurements of friction in the presence of molecularly thin lubricant layers and suggests that a molecularly thin lubricant bearing could be successfully used to reduce solid substrate damage at the interface.

Designing metainterfaces with specified friction laws

“…1 is expected to be applicable to a large variety of frictional interfaces, the following scientific and technological choices represent only one example of how our design strategy can be implemented. First, we chose to work with contacts between polydimethylsiloxane (PDMS) and glass (26), a widely used pair of materials in contact mechanics and friction studies (1,11). The behavior of sheared PDMS-glass, single sphereplane contacts has been extensively characterized recently (27)(28)(29)(30), which provides useful insights into the single-asperity laws that should be used in the friction model.…”

“…espite centuries of investigation, a comprehensive understanding of friction is still lacking. For instance, predicting from first principles the value of the friction force, F, of a given dry contact interface remains out of reach, mainly because of the multiscale character of surfaces and the multiphysics nature of contact interactions (1). Thus, time-and resource-consuming experimental tests remain necessary to calibrate the frictional behavior of a contact interface as soon as any change is brought to the material pair, shape of the solids, loading conditions, surface finish, or environmental conditions.…”

“…At the present time, surface functionalization is the main approach that is followed worldwide to provide contact interfaces with improved frictional capabilities (1,10). It often consists of creating a certain surface topography at various length scales or adding a homogeneous or heterogeneous thin coating at the solid surface.…”

Equivalent characteristic model of a rough contact interface based on virtual material method

“…The element was made up of two adjusted Iwan models, and owned the typical free degrees of the displacement and rotation. In 2012, using a dynamic model of experimental system, Vakis and Polycarpou 22 assumed that a rough contact interface of the tested structural system was a virtual subsystem, and obtained the characteristic parameters for the rough contact interface. In 2017, Lee et al 23 studied experimentally on the contact behavior of micro/nano devices, and verified the analysis results of other statistical methods by the obtained experimental results.…”