Multiscale analysis of friction behavior at fretting interfaces
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ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Multiscale analysis of friction behavior at fretting interfaces Zhinan ZHANG1,*, Shuaihang PAN2, Nian YIN1, Bin SHEN1, Jie SONG3 1
State Key Laboratory of Mechanical Systems and Vibrations, Shanghai Jiao Tong University, Shanghai 200240, China
2
School of Mechanical & Aerospace Engineering, University of California Los Angeles, Los Angeles 90095, USA
3
Institute of Nano Biomedicine and Engineering, Shanghai Jiao Tong University, Shanghai 200240
Received: 20 June 2019 / Revised: 19 September 2019 / Accepted: 13 November 2019
© The author(s) 2019. Abstract: Friction behavior at fretting interfaces is of fundamental interest in tribology and is important in material applications. However, friction has contact intervals, which can accurately determine the friction characteristics of a material; however, this has not been thoroughly investigated. Moreover, the fretting process with regard to different interfacial configurations have also not been systematically evaluated. To bridge these research gaps, molecular dynamics (MD) simulations on Al–Al, diamond–diamond, and diamond–silicon fretting interfaces were performed while considering bidirectional forces. This paper also proposes new energy theories, bonding principles, nanoscale friction laws, and wear rate analyses. With these models, semi-quantitative analyses of coefficient of friction (CoF) were made and simulation outcomes were examined. The results show that the differences in the hardness, stiffness modulus, and the material configuration have a considerable influence on the fretting process. This can potentially lead to the force generated during friction contact intervals along with changes in the CoF. The effect of surface separation can be of great significance in predicting the fretting process, selecting the material, and for optimization. Keywords: molecular dynamics simulation; friction; wear; fretting
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Introduction
Crystalline materials, such as metallic crystals and atomic crystals, can have a broad niche of applications for their distinctive properties. For example, aluminum (Al) is a typical and important metallic crystal that is often used as the base material in many essential parts in spacecraft [1–4], automobiles, and electronics such as batteries and triboelectric nanogenerators [5, 6]. This can be attributed to the high performance, good utility, and relatively low cost of aluminum. On the other hand, diamond and silicon (Si) are two traditional materials with high hardness atomic crystals. They are also commonly used in metal processing, coating, and protection [7, 8]. These materials, owing to their small-scale surface roughness (1–1,000 nm), inevitably suffer from micro-scale motions, i.e., the
fretting process, when they form interfaces under normal service [9, 10]. Theories such as the stick–slip effect [11, 12] can help in the understanding of the fretting phenomena. However, the fretting process for Al, Si, and diamond, until recently, has not been fully understood by the char
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