Friction between solids

Abstract

The theoretical examination of the friction between solids is discussed with a focus on self-assembled monolayers, carbon-containing materials and antiwear additives. Important findings are illustrated by describing examples where simulations have complemented experimental work by providing a deeper understanding of the molecular origins of friction. Most of the work discussed herein makes use of classical molecular dynamics (MD) simulations. Of course, classical MD is not the only theoretical tool available to study friction. In view of that, a brief review of the early models of friction is also given. It should be noted that some topics related to the friction between solids, i.e. theory of electronic friction, are not discussed here but will be discussed in a subsequent review.

Theoretical Approaches for Understanding the Interplay Between Stress and Chemical Reactivity

“…The use of static simulation methods to study the changes in energy and structure that occur during tribochemical processes has a long history [48,49]. These methods have been used to optimize the reactants and products of tribochemical reactions, to examine the PES associated with the movement of surfaces relative to one another, and to identify the MEPs connecting the reactants and products of tribochemical reactions.…”

“…However, the stress-induced processes involving bulk systems have been modeled extensively in the context of tribology, which is the study of friction, wear, and lubrication [48,49]. As such, potential exists to apply existing techniques used to study systems such as sliding contacts in the context of the mechanochemical activation of reactions occurring in bulk systems where shear and compressive stresses play key roles in activating reactions.…”

Influence of chain ordering on frictional properties of self-assembled monolayers (SAMs) in nano-lubrication

“…For example, conventional molecular dynamics simulations and AFM or CFM experiments differ in 6 orders of magnitude or more in their time scales [109]. This gap is expected to narrow with continued development in experimental methods to probe the interface during sliding at smaller and smaller length scales, and with increases in computational power and algorithm development to increase the time and length scales of simulations [142]. More fundamental understanding of the frictional properties of SAMs can be obtained with continued efforts in these areas.…”

“…To this end, atomistic computer simulations provide a powerful, and in some cases essential tool for understanding the molecular behaviors of SAMs. Molecular dynamics simulations can give unique atomic-scale insights into processes that occur at the sliding interfaces and the frictional response of SAMs that cannot be obtained from experimental observations [142][143][144].…”

A review of friction models in interacting joints for durability design

“…In classical modelling, the effect of friction is not considered. However, friction is defined as the tangential reaction force that occurs between two surfaces in contact, dependent on factors that include the contact geometry, the topology, relative velocity of surfaces in contact and displacement of surfaces, load and lubrication [23,[68][69][70][71]. Friction is a complex phenomenon caused by the interaction of the surface and near surface regions of two interacting components as well as lubricants if present between such surfaces [72].…”