Elastohydrodynamic lubricant flow with nanoparticle tracking

Abstract

Lubricants operating in elastohydrodynamic (EHD) contacts exhibit local variations in rheological properties when the contact pressure rises.

Shear heating, flow, and friction of confined molecular fluids at high pressure

“…23 For example, comprehensive confined NEMD simulations have studied the shear heating, flow, and friction behavior of atomic Lennard-Jones (LJ) fluids at high P andγ. [24][25][26] As observed experimentally, [18][19][20] transitions between Couette flow and different forms of shear localization were reported as P was increased. [24][25][26] Shear localization has also been observed in NEMD simulations of many other fluids such as model glasses 27 and entangled polymer melts.…”

“…5 Such extreme conditions are diffi-viscous polymer films at high P. [15][16][17] More recently, shear localization has been observed in thinner (≈ 1 µm) viscous polymer films under conditions more representative of EHL using in situ photoluminescence techniques. [18][19][20] However, such behavior has not yet been demonstrated experimentally using both representative EHL conditions and fluids similar to commercial lubricants. 5 Lubricants are designed to give low EHL friction to minimize energy losses while traction fluids should give consistently high friction for use in continuously variable transmissions.…”

Contributions of Molecular Dynamics Simulations to Elastohydrodynamic Lubrication

“…However, recent experiments have highlighted that the through-thickness velocity profiles in some systems can show significant deviations from linearity under EHL conditions. Some experiments have shown that the central region can become solid-like and flow more slowly than the liquid-like region close to the surfaces, which is often referred to as plug slip or plug flow [88][89][90]. Experiments for different systems and conditions have shown that the fluid close to the surfaces can become solid-like and flow more slowly than the liquid-like central region, which is known as central localisation or shear banding [91][92][93].…”

A study of thermal effects in EHL rheology and friction using infrared microscopy

“…Wong and co-workers [47][48] [49] proved the existence of shear bands at high pressure with the use of luminescence velocimetry methods by observing through-thickness velocity profiles of lubricants. Using the uniform shear stress assumption across the oil film, they showed a phase transition and lubricant viscosity rise occurring at high pressure and generating a non-linear velocity profile.…”