The influence of the complex material behavior of thermoplastic polymers in lubricated contacts is poorly understood. It affects the optimal design of power-transmitting thermoplastic machine elements and the exploitation of its potential, e.g., lightweight design, low-noise operation, and cost-effective manufacturing when injection-molded. This study applies the in situ thin-film sensor technology on a twin-disk tribometer in order to study the elastohydrodynamic lubrication of rolling-sliding contacts with the thermoplastic polymer polyetheretherketone. The results provide insights into the effects and relevance of its thermoplastic material properties. Pressure measurements reveal a typical hydrodynamic profile in combination with a large deformation of the contact zone. The influence of speed and slip ratio is thereby negligible. The temperature rise is low compared to elastohydrodynamically lubricated contacts with steel and is mainly influenced by the slip ratio as well as the load, whereas speed plays a subordinated role. In general, the heat generation is governed by shearing and backflow in the contact inlet zone at low slip ratios and shearing in the contact zone at high slip ratios. No effects attributed to viscoelasticity or loading frequency were observed at the operating conditions considered.
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http://dx.doi.org/10.3390/polym14204398 | DOI Listing |
Sci Rep
December 2024
School of architecture, Ocean and energy power engineering, Wuhan University of Technology, Wuhan, 430070, China.
During maritime operations, extreme events such as explosions, grounding, and seal failures can cause water ingress into lubricant compartments, forming oil-water emulsions that significantly affect the lubrication performance of ship stern bearings. Existing studies mainly focus on low water content, with limited exploration of the impact of high water content on lubrication performance. To address this gap, viscosity measurements of oil-water mixtures were conducted, and an emulsification viscosity equation applicable to varying water contents was derived.
View Article and Find Full Text PDFSoft Matter
November 2024
Laboratoire de Physique de lEcole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France.
In confinement, liquid flows are governed by a complex interplay of molecular, viscous and elastic forces. When a fluid is confined between two approaching surfaces, a transition is generally observed from a long range dynamical response dominated by viscous forces in the fluid to a short range elasto-hydrodynamic response due to the elastic deformation of the solid materials. This study investigates the behavior of fluids driven between oscillating solid surfaces using a dynamic Surface Force Apparatus.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
October 2024
Univ. Bordeaux, CNRS, LOMA, UMR 5798, Talence F-33400, France.
Langmuir
May 2024
School of Engineering College of Engineering and Physical Sciences, University of Birmingham, Birmingham B15 2TT, West Midlands, U.K.
This study presents new insights into the potential role of polyelectrolyte interfaces in regulating low friction and interstitial fluid pressurization of cartilage. Polymer brushes composed of hydrophilic 3-sulfopropyl methacrylate potassium salt (SPMK) tethered to a PEEK substrate (SPMK--PEEK) are a compelling biomimetic solution for interfacing with cartilage, inspired by the natural lubricating biopolyelectrolyte constituents of synovial fluid. These SPMK--PEEK surfaces exhibit a hydrated compliant layer approximately 5 μm thick, demonstrating the ability to maintain low friction coefficients (μ ∼ 0.
View Article and Find Full Text PDFPhys Rev Lett
February 2024
Department of Mathematics, Mechanics Division, University of Oslo, Oslo 0316, Norway.
Pockets of viscous fluid coalescing beneath an elastic sheet are encountered in a wide range of natural phenomena and engineering processes, spanning across scales. As the pockets merge, a bridge is formed with a height increasing as the sheet relaxes. We study the spatiotemporal dynamics of such an elastohydrodynamic coalescence process by combining experiments, lubrication theory, and numerical simulations.
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