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    Quantitative understanding of single-asperity contact via molecular simulations

    Author
    Yang, Yongjian
    View/Open
    178539_Yang_rpi_0185E_11121.pdf (6.301Mb)
    Other Contributors
    Shi, Yunfeng; Huang, Liping; Blanchet, Thierry A.; Schadler, L. S. (Linda S.); Samuel, Johnson;
    Date Issued
    2017-08
    Subject
    Materials engineering
    Degree
    PhD;
    Terms of Use
    This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.;
    Metadata
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    URI
    https://hdl.handle.net/20.500.13015/2043
    Abstract
    Single-asperity contact is a critical topic in nanotechnology, not only its technical relevance in terms of reliability in probe-based characterization instruments and memory storage devices, but also its fundamental importance as a pathway to multi-asperity contact. Recent experimental studies using AFM have discovered a new wear mechanism named atomic wear. However, the atomic level understanding of the nanoscale wear mechanism is still lacking due to experimental challenges such as precise measurements of wear rates. Aside from debris generation, single- asperity contact can also cause plasticity and/or cracking. For instance, the critical crack initiation in metallic glass under nanoindentation is yet not understood at an atomic level.; In this thesis, I investigated single-asperity sliding and nanoindentation using molecular simulations. By tuning the interfacial adhesion and contact stress, it was found that there are two distinct wear modes (atomic wear and plastic wear) in terms of mathematical formulation, debris spatial orientation, and debris cluster size distribution. The transition from plastic wear to atomic wear can be also enhanced by adding lubricant. By controlling the sliding temperature, velocity and contact area, we found that atomic wear is shear-assisted, athermally-activated, and re- depositable. In a cluster analysis of atomic wear, we demonstrate a scaling behavior of the cluster distribution, which can be analogically understood by the critical phenomenon of phase transition. Through nanoindentation simulations, the crack initiation mechanism within a glassy material was revealed. The atomic insights obtained from our simulations will improve the quantitative reliability assessment for probe-based devices, help develop new crack resistant materials, and pave the way to quantitatively understand macroscopic wear and cracking.;
    Description
    August 2017; School of Engineering
    Department
    Dept. of Materials Science and Engineering;
    Publisher
    Rensselaer Polytechnic Institute, Troy, NY
    Relationships
    Rensselaer Theses and Dissertations Online Collection;
    Access
    Restricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.;
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    • RPI Theses Online (Complete)

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