Rough Surface Interactions of Micro/nano-Scale Contact Systems
Yeo, Chang-Dong
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https://hdl.handle.net/2142/83911
Description
Title
Rough Surface Interactions of Micro/nano-Scale Contact Systems
Author(s)
Yeo, Chang-Dong
Issue Date
2008
Doctoral Committee Chair(s)
Polycarpou, Andreas A.
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
In this work, three major issues of miniature systems in regards to contact behavior have been studied. First, nanomechanical properties of ultra-thin carbon films such as hardness and elastic modulus have been investigated using a newly developed nanoindentation technique and custom-built high-resolution nanoindentation system, which enabled reliable measurements of hardness and elastic modulus at contact depths below 1 nm. It was observed that the thicker carbon film showed lower hardness and elastic modulus values. Second, an improved rough surface contact model suitable for miniature systems has been developed accounting for both asperity and substrate deformation during contact. Compared to a representative asperity-based contact model, it was found that the proposed model is closer to actual contacts of a miniature system. Third, experimental measurements of dynamic interactive forces such as pull-in and pull-off force have been performed using a newly developed instrument, where two piezo-electric actuators were used to control normal and tangential motions of the contacting bodies and the interactive forces were measured from a capacitive high-resolution force transducer. The measured interactive forces were examined in regards to various dynamic conditions. It was observed that the slower approaching velocity showed earlier jump-in behavior with higher pull-in force and the slower retracting showed later jump-out behavior and higher pull-off force. Moreover, the horizontal motion of the contacting surfaces leaded to reduction of pull-off force under dry contact condition, whereas it leaded to increase of higher pull-off force under partial wet condition.
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