Friction, slip and structural inhomogeneity of the buried interface

Abstract

An atomistic model of metallic contacts using realistic interatomic potentials is used to study the connection between friction, slip and the structure of the buried interface. Incommensurability induced by misalignment and lattice mismatch is modeled with contact sizes that are large enough to observe superstructures formed by the relative orientations of the surfaces. The periodicity of the superstructures is quantitatively related to inhomogeneous shear stress distributions in the contact area, and a reduced order model is used to clarify the connection between friction and structural inhomogeneity. Finally, the movement of atoms is evaluated before, during and after slip in both aligned and misaligned contacts to understand how the interfacial structure affects the mechanisms of slip and the corresponding frictional behavior.

Analytical Models for Atomic Friction

“…For example, for a lattice mismatch of b/a = 4/5, a minimum friction will occur at N = 5, 10, and so on. Another observation is that, for any value of Nb/a, although the local friction minima arise only at some magic sizes, over a long range the friction increases linearly with the contact area [76]. The friction comes from the viscous force which is proportional to sliding speed.…”

Molecular dynamics simulation of atomic friction: A review and guide

“…This explains why essentially all stable stick-slip observed in AFM measurements on metal surfaces have been conducted on the (111) surface of FCC metals 2,30,47,49 and most simulations are designed correspondingly. 30,56,57 Some materials exhibit longer range (larger than the atomic lattice) surface features, which also affect friction. For example, herringbone reconstruction on the Au(111) surface 58 has been shown to modulate friction in distinct ways.…”

“…However, this concept becomes inadequate when structure and stress inhomogeneity are considered. If the tip and substrate surfaces are not perfectly aligned, stress inhomogeneity could cause partial slip in which a subset of the contacting surface moves first; 56,57,77 partial slip is in contrast to uniform slip where all the atoms in the contact move forward at once. Further, the displacement of the atoms coincides with the accumulation or relief of the shear stress, which implies that structural inhomogeneity is directly related to partial slip.…”

Electrostatic precursors to granular slip events

“…On the large scale, these transitions manifest themselves in catastrophic geological slip events (2)(3)(4), and on the small scale, they are intimately associated with fracture (5) and material inhomogeneities (6,7) , causing a documented 50% rejection rate of manufactured ceramics (8,9). In this letter, we show for the first time that electrical precursors are strongly correlated with-and often precede-any outward sign of a slip event in a powder bed.…”