Date

2017

Document Type

Thesis

Degree

Master of Science

Department

Mechanical Engineering

First Adviser

Krick, Brandon A.

Abstract

In this paper, we zoom in on the points of contact between the two materials in order to truly understand the surface-to-surface interface. We choose aluminum oxide (Ruby/Sapphire) spheres and polydimethylsiloxane (PDMS) discs to investigate the variability of real adhesive contact. An in-situ optical tribometer is built and implemented for use in obtaining forces of adhesion between PDMS and Ruby and comparing against the Johnson-Kendall-Roberts (JKR) contact model. Adhesion hysteresis is explored and compared to results found in the literature. High resolution in-situ imagery is coupled with custom data acquisition software to examine the relationship of contact area to applied force, loading rate, dwell time, and unloading rate. Contact area and pull-off force are shown to be dependent on applied force, dwell time, and unloading rate, while loading rate shows no major effect. Newton Rings in captured in-situ contact images are used to create three-dimensional models and height maps of the tensile region. This method provides accurate representations of surface and bulk behavior in a variety of contact conditions. A tensile zone is found at the edge of contact for all testing scenarios.

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