Fundamental mechanisms of interfacial friction. 2. Stick-slip friction of spherical and chain molecules

Two-dimensional observation of drainage and layering transitions in confined liquids

“…In an ideal system, two-dimensional density fluctuations in the metastable layer lead to small holes. Sufficiently large holes (critical nuclei with r c :15 A , ) are stabilized by the elastic relaxation of the compressed mica substrates and mobility at a film thickness of a few molecular diameters [15][16][17][18]. However, thin films of chain alcohols behave differently.…”

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

“…[21][22][23] The precise details of these physical changes are not well characterised, and could well vary from system to system. 24,25 NEMD simulations of Lei and Leng, 18 on monatomic molecules indicated that the ordering-disordering transition takes place within the layers parallel to the wall, and that the stick-slip events originate from relative sliding of adjacent layers, and the layer next to the wall with the wall.…”

Shear-band arrest and stress overshoots during inhomogeneous flow in a metallic glass

“…Whilst this work directly reveals shear-band creep, as well as static aging after shear-band arrest, we also observe a pronounced time dependence of the stress-overshoot magnitude. From analogous stop-and-start experiments on confined nanoscopic liquids, we relate the stress-overshoot magnitude to a characteristic nucleation time of a liquidlike to solidlike transition, [24][25][26][27] and propose that this governs shear-band arrest. Such an approach may provide the key ingredients to fundamentally understanding the stable plastic flow of metallic glasses.…”

“…This result is analogous to the time dependency of stiction-spike magnitudes of confined nanoscopic liquids and glassy polymer interfaces, in which this characteristic time is attributed to the time necessary to nucleate a solidlike state from a liquidlike state that prevails during sliding. [24][25][26][27] Note at this stage that by employing a framework known for static friction experiments of nanoscopic confined liquids, we naturally assume the operating shear-band to be a planar defect with strongly reduced viscosity as compared to the surrounding bulk matrix. This assumption is well supported by recent results investigating shear-band properties in bulk metallic glasses.…”

“…We will now proceed with comparing the here-obtained s n with the inherent time scales of serrated flow at higher temperatures obtained in our earlier work 10,11,13 and propose why shear bands arrest by developing the analogy borrowed from static friction experiments of confined liquids. [24][25][26][27] To do this, it is important to point out that the process of a displacement jump during serrated flow has been described by taking into account the time Dt over which the increment in displacement Du is created (schematic inset in Fig. 4).…”