# Molecular Origin of Limiting Shear Stress of Elastohydrodynamic Lubrication Oil Film Studied by Molecular Dynamics

## TL;DR

This study uses molecular dynamics simulations to investigate how pressure influences the shear stress and phase transition in elastohydrodynamic lubrication oil films, revealing a transition from viscoelastic to plastic-elastic behavior.

## Contribution

It provides molecular-level insights into the pressure-induced phase transition affecting shear stress in lubrication films, which was previously understood only experimentally.

## Key findings

- Transition in traction behavior around 0.5--2.0 GPa
- Suppression of molecular motion fluctuations at transition
- Correlation between phase change and shear stress increase

## Abstract

All-atom molecular dynamics simulations of an elastohydrodynamic lubrication oil film are performed to study the effect of pressure. Fluid molecules of n-hexane are confined between two solid plates under a constant normal force of 0.1--8.0 GPa. Traction simulations are performed by applying relative sliding motion to the solid plates. A transition in the traction behavior is observed around 0.5--2.0 GPa, which corresponds to the viscoelastic region to the plastic--elastic region, which are experimentally observed. This phase transition is related to the suppression of the fluctuation in molecular motion.