Precise Correlation of Contact Area and Forces in the Unstable Friction between a Rough Fluoroelastomer Surface and...

Area of Science:

• Tribology
• Materials Science
• Surface Engineering

Background:

• Stick-slip friction in elastomers is influenced by adhesion, strain, surface roughness, and energy dissipation.
• Understanding elastomer friction dynamics is crucial for applications like seals and tires.
• In situ techniques are needed to link real contact area with interfacial forces during elastomer sliding.

Purpose of the Study:

• To investigate the stick-slip friction behavior of a machined fluoroelastomer (FKM) against glass.
• To analyze the evolution of the real contact area during sliding using in situ optical methods.
• To determine the influence of sliding velocity on stick-slip dynamics and friction.

Main Methods:

• In situ optical microscopy to capture real-time contact area evolution.
• Sliding a machined FKM hemisphere against glass over a velocity range of 1 µm/s to 100 µm/s.
• Image analysis using Otsu's method for thresholding and machine learning for motion delineation.

Main Results:

• Observed local pinned and partial slip regions within the macroscale sticking phase, contributing to friction.
• Identified a critical sliding velocity where stick-slip motion transitioned from high-frequency/low-amplitude to low-frequency/high-amplitude.
• Demonstrated a correlation between changes in contact area and friction behavior before and during pinning and slip.

Conclusions:

• The study provides a multi-technique approach to understand elastomer friction at a microscale level.
• Findings offer insights into contact evolution and friction mechanisms in viscoelastic materials.
• Results can inform the development of improved friction models for elastomers in dynamic applications.