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Understanding the Effects of Multi-scale Surface Roughness on the Contact Properties of Hard-Material Interfaces

Thimons, Luke A. (2022) Understanding the Effects of Multi-scale Surface Roughness on the Contact Properties of Hard-Material Interfaces. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Adhesion between rough surfaces is an important property of interfaces and is one that has far-reaching implications. Decades of experimental and theoretical work on the topic of adhesion between rough surfaces has been carried out. Yet no comprehensive understanding has emerged of the complex relationship between surface roughness and adhesion. From early measurements and models treating surfaces as nominally smooth to modern attempts to capture the fractal nature of real surfaces, we have yet to develop a robust connection between roughness and adhesion. This work focuses on clarifying the complicated relationship between surface roughness and dry adhesion, specifically in hard materials with tech-relevant applications. Experimental measurements of large-scale adhesion on a custom micro-mechanical tester are paired with extensive roughness characterization, spanning many orders of magnitude in size. Together, these give insight into fundamental parameters of interfacial interactions, and shed light on which scales of roughness play the most significant role in adhesion in different conditions.
There are three primary scientific contributions from this body of work. First, an in-depth analysis is presented of how to describe and characterize multi-scale roughness. Specifically, an analysis was performed (described in Chapter 3) of three commonly used metrics (the power spectral density, the autocorrelation function, and variable bandwidth methods), and their advantages and disadvantages of describing surfaces for the purpose of prediction of surface properties. Second, an experimental analysis was performed into the roughness-dependent adhesion between technologically relevant coatings, nanocrystalline diamond and aluminum oxide (ruby), to determine which length scales most strongly control adhesion. Specifically, this work has revealed a larger-than-expected interaction range for these surfaces, and a limited range of size scales that contribute most significantly to adhesion. Third, the scientific understanding of roughness-dependent adhesion is advanced by lithographically patterning surfaces into silicon to intentionally vary different size scales and determine the contribution of each. The results from this last investigation underscore the importance of size scale in linking topography to adhesion and demonstrate how interatomic interactions determine the range of size scales that impact adhesion.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Thimons, Luke A.lat55@pitt.edulat550000-0003-4511-1807
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorJacobs, Tevis
Committee MemberLee,
Committee MemberBeschorner,
Committee MemberLiu,
Date: 16 January 2022
Date Type: Publication
Defense Date: 27 October 2021
Approval Date: 16 January 2022
Submission Date: 26 October 2021
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 182
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Materials Science and Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: adhesion;roughness;contact mechanics;tribology;contact properties
Date Deposited: 16 Jan 2022 18:35
Last Modified: 16 Jan 2023 06:15


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