Rotation-translation coupling of soft objects in lubricated contact

Area of Science:

• Fluid Dynamics and Tribology
• Soft Matter Physics
• Contact Mechanics

Background:

• Understanding the interplay between fluid lubrication and elastic deformation is crucial in micro-scale contact mechanics.
• The behavior of submerged bodies in contact with soft surfaces is relevant to biological systems and micro-devices.

Purpose of the Study:

• To analyze the coupled rotational and translational motion of a submerged cylinder on a soft elastic substrate.
• To investigate the influence of substrate deformation and fluid film thickness on contact dynamics.
• To explore how external torque affects the motion, including back-spinning and top-spinning states.

Main Methods:

• Employed numerical solutions to model the elastohydrodynamic lubrication problem.
• Utilized asymptotic theory to analyze the system across various deformation regimes.
• Investigated the entire range of substrate deformations relative to the fluid film thickness.

Main Results:

• A strong coupling between rotation and translation was observed when substrate deformation is comparable to fluid film thickness.
• In large deformation limits, near-Hertzian contact and slip-free rolling occur, similar to dry friction.
• For small deformations, weaker coupling results in rotation rate scaling with translation speed to the one-third power.

Conclusions:

• The study reveals complex coupling dynamics between rotation and translation in lubricated contact.
• External torque can induce distinct rotational and translational states, demonstrating robust behavior across substrate thicknesses.
• Findings provide insights into micro-scale tribology and the mechanics of soft interfaces.