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Hard‐material Adhesion: Which Scales of Roughness Matter?

Thimons, Luke and Gujrati, Abhijeet and Sanner, Antoine and Pastewka, Lars and Jacobs, Tevis (2020) Hard‐material Adhesion: Which Scales of Roughness Matter? Experimental Mechanics. ISSN 0014-4851

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Background Surface topography strongly modifies adhesion of hard-material contacts, yet roughness of real surfaces typically exists over many length scales, and it is not clear which of these scales has the strongest effect. Objective: This investigation aims to determine which scales of topography have the strongest effect on macroscopic adhesion.
Methods Adhesion measurements were performed on technology-relevant diamond coatings of varying roughness using spherical ruby probes that are large enough (0.5-mm-diameter) to sample all length scales of topography. For each material, more than 2000 measurements of pull-off force were performed in order to investigate the magnitude and statistical distribu- tion of adhesion. Using sphere-contact models, the roughness-dependent effective values of work of adhesion were measured, ranging from 0.08 to 7.15 mJ/m2 across the four surfaces. The data was more accurately fit using numerical analysis, where an interaction potential was integrated over the AFM-measured topography of all contacting surfaces.
Results These calculations revealed that consideration of nanometer-scale plasticity in the materials was crucial for a good quantitative fit of the measurements, and the presence of such plasticity was confirmed with AFM measurements of the probe after testing. This analysis enabled the extraction of geometry-independent material parameters; the intrinsic work of adhesion between ruby and diamond was determined to be 46.3 mJ/m2. The range of adhesion was 5.6 nm, which is longer than is typically assumed for atomic interactions, but is in agreement with other recent investigations. Finally, the numerical analysis was repeated for the same surfaces but this time with different length-scales of roughness included or filtered out. Conclusions The results demonstrate a critical band of length-scales—between 43 nm and 1.8 μm in lateral size—that has the strongest effect on the total adhesive force for these hard, rough contacts.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Thimons, Lukelat55@Pitt.edulat550000-0003-4511-1807
Gujrati, Abhijeetabg30@Pitt.eduabg300000-0001-7744-5743
Sanner, Antoineantoine.sanner@imtek.uni-freiburg.de0000-0002-7019-2103
Pastewka, Larslars.pastewka@imtek.uni-freiburg.de0000-0001-8351-7336
Jacobs, Tevistjacobs@Pitt.edutjacobs0000-0001-8576-914X
Date: 9 December 2020
Date Type: Publication
Journal or Publication Title: Experimental Mechanics
Publisher: Springer
DOI or Unique Handle: 10.1007/s11340-021-00733-6
Schools and Programs: Swanson School of Engineering > Mechanical Engineering and Materials Science
Refereed: Yes
Uncontrolled Keywords: Adhesion, Nanocrystalline diamond, Multi-scale surface roughness, Range of adhesion, Pull-off force
ISSN: 0014-4851
Official URL:
Article Type: Research Article
Date Deposited: 26 Jul 2021 19:47
Last Modified: 26 Jul 2021 19:47


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