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We study theoretically and numerically the kinetics of the coefficient of friction of an elastomer due to abrupt changes of sliding velocity. Numerical simulations reveal the same qualitative behavior which has been observed experimentally on different classes of materials: the coefficient of friction first jumps and then relaxes to a new stationary value. The elastomer is modeled as a simple Kelvin body and the surface as a self-affine fractal with a Hurst exponent in the range from 0 to 1. Parameters of the jump of the coefficient of friction and the relaxation time are determined as functions of material and loading parameters. Depending on velocity and the Hurst exponent, relaxation of friction with characteristic length or characteristic time is observed.
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http://dx.doi.org/10.1038/srep05795 | DOI Listing |
Ultrasonics
March 2025
Electronics Research Laboratory, University of Helsinki, Helsinki, Finland.
In many industrial processes, accumulation of fouling can lead to decreased production efficiency by weakening the flow in pipes or causing additional friction on the ships' hulls. To detect the fouled areas for descaling, ultrasonic guided waves (UGWs) can be utilized. Usually, this is carried out by coupling phased array collars of contact transducers onto the pipe.
View Article and Find Full Text PDFNanotechnology
March 2025
Xi'an Jiaotong University, Xi'an, Xi'an, Shaanxi, 710049, CHINA.
The wear and corrosion resistance of water-based polytetrafluoroethylene (PTFE) coating need to be further improved to cope with various harsh environmental conditions. In this paper, a mulberry-like ZSM-5 molecular sieve was prepared and then was modified to enhance the uniformity, wear resistance and hardness of PTFE coating. In addition, a ZSM-5/MoS2/PTFE coating was prepared by adding MoS2 in the chemical composition of coatings, which significantly increased the critical cracking thickness of PTFE to 27 μm.
View Article and Find Full Text PDFLangmuir
March 2025
State Key Laboratory of Solidification Processing, Center of Advanced Lubrication and Seal Materials, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China.
Herein, functionalized carbon aerogel microspheres (CAMs) were successfully prepared by the pyrolysis of resorcinol-formaldehyde (RF) microspheres followed by surface modification. First, RF microspheres were carbonized to obtain CAMs. Afterward, the polyphenolic compound of epigallocatechin gallate (EGCG) was reacted with melamine to form a poly(EGCG) layer onto the CAM surface, followed by bonding the antiwear molecule dialkyl dithiophosphate (DDP) by the Michael addition, resulting in DDP-functionalized CAMs (DDP-CAMs).
View Article and Find Full Text PDFJ Phys Chem Lett
March 2025
Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel.
The mechanisms underlying chemifriction (the contribution of interfacial bonding to friction) in defected twisted graphene interfaces are revealed using fully atomistic molecular dynamics simulations based on machine-learning potentials. This involves stochastic events of consecutive bond formation and rupture between single vacancy defects that may enhance friction. A unique shear-induced interlayer atomic transfer healing mechanism is discovered that can be harnessed to design a run-in procedure to restore superlubric sliding.
View Article and Find Full Text PDFMaterials (Basel)
March 2025
School of Mechanical Science and Engineering, Northeast Petroleum University, Daqing 163318, China.
At present, the improvement of anti-wear performance of piston rings remains a challenge. In this article, Ni-SiC composite coatings fabricated at 3, 9, and 15 g/L SiC were denoted as NSc-3, NSc-9, and NSc-15 coatings. Meanwhile, the influence of SiC concentration on the surface morphology, phase structure, microhardness, and anti-wear performance of electrodeposited Ni-SiC composite coatings were investigated utilizing scanning electron microscopy, X-ray diffraction, a microhardness tester, and a friction-wear tester, respectively.
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