Mechanisms of Friction Reduction in Longitudinal Ultrasonic Surface Haptic Devices with Non-Collinear Vibrations and Finger Displacement

The Rotating Liner Engine (RLE) concept is a design concept for internal combustion engines, where the cylinder liner rotates at a surface speed of 2–4 m/s in order to assist piston ring lubrication. Specifically, we have evidence from prior art and from our own research that the above rotation has the potential to eliminate the metal-to-metal contact/boundary friction that exists close to the piston reversal areas. This frictional source becomes a significant energy loss, especially in the compression/expansion part of the cycle, when the gas pressure that loads the piston rings and skirts is high. This paper describes the Diesel RLE prototype constructed from a Cummins 4BT and the preliminary observations from initial low load testing. The critical technical challenge, namely the rotating liner face seal, appears to be operating with negligible gas leakage and within the hydrodynamic lubrication regime for the loads tested (peak cylinder pressures of the order of 100 bar) and up to about 10 bar BMEP (brake mean effective pressure). Preliminary testing has proven that the metal-to-metal contact in the piston assembly mostly vanished, and a friction reduction at idle conditions of about 40% as extrapolated to a complete engine has taken place. It is expected that as the speed increases, the friction reduction percentage will diminish, but as the load increases, the friction reduction will increase. The fuel economy benefit over the US Heavy-Duty driving cycle will likely be of the order of 10% compared to a standard engine.

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On the Microstructural, Mechanical and Tribological Properties of Mo-Se-C Coatings and Their Potential for Friction Reduction against Rubber

Materials ◽

10.3390/ma14061336 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1336

Author(s):

Jorge Caessa ◽

Todor Vuchkov ◽

Talha Bin Yaqub ◽

Albano Cavaleiro

Keyword(s):

Carbon Content ◽

Friction And Wear ◽

Current Mode ◽

Friction Reduction ◽

Transition Metal Dichalcogenide ◽

Butadiene Rubber ◽

Wear Rates ◽

Mechanical And Tribological Properties ◽

The Coefficient Of Friction ◽

Pin On Disk

Friction and wear contribute to high energetic losses that reduce the efficiency of mechanical systems. However, carbon alloyed transition metal dichalcogenide (TMD-C) coatings possess low friction coefficients in diverse environments and can self-adapt to various sliding conditions. Hence, in this investigation, a semi-industrial magnetron sputtering device, operated in direct current mode (DC), is utilized to deposit several molybdenum-selenium-carbon (Mo-Se-C) coatings with a carbon content up to 60 atomic % (at. %). Then, the carbon content influence on the final properties of the films is analysed using several structural, mechanical and tribological characterization techniques. With an increasing carbon content in the Mo-Se-C films, lower Se/Mo ratio, porosity and roughness appeared, while the hardness and compactness increased. Pin-on-disk (POD) experiments performed in humid air disclosed that the Mo-Se-C vs. nitrile butadiene rubber (NBR) friction is higher than Mo-Se-C vs. steel friction, and the coefficient of friction (CoF) is higher at 25 °C than at 200 °C, for both steel and NBR countersurfaces. In terms of wear, the Mo-Se-C coatings with 51 at. % C showed the lowest specific wear rates of all carbon content films when sliding against steel. The study shows the potential of TMD-based coatings for friction and wear reduction sliding against rubber.

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Fast laser surface texturing of spherical samples to improve the frictional performance of elasto-hydrodynamic lubricated contacts

Friction ◽

10.1007/s40544-020-0462-4 ◽

2021 ◽

Author(s):

G. Boidi ◽

P. G. Grützmacher ◽

A. Kadiric ◽

F. J. Profito ◽

I. F. Machado ◽

...

Keyword(s):

Surface Texturing ◽

Hydrodynamic Pressure ◽

Friction Reduction ◽

Laser Surface Texturing ◽

Textured Surfaces ◽

Engineering Applications ◽

Lubricated Contacts ◽

Fluid Uptake ◽

Direct Laser ◽

Frictional Performance

AbstractTextured surfaces offer the potential to promote friction and wear reduction by increasing the hydrodynamic pressure, fluid uptake, or acting as oil or debris reservoirs. However, texturing techniques often require additional manufacturing steps and costs, thus frequently being not economically feasible for real engineering applications. This experimental study aims at applying a fast laser texturing technique on curved surfaces for obtaining superior tribological performances. A femtosecond pulsed laser (Ti:Sapphire) and direct laser interference patterning (with a solid-state Nd:YAG laser) were used for manufacturing dimple and groove patterns on curved steel surfaces (ball samples). Tribological tests were carried out under elasto-hydrodynamic lubricated contact conditions varying slide-roll ratio using a ball-on-disk configuration. Furthermore, a specific interferometry technique for rough surfaces was used to measure the film thickness of smooth and textured surfaces. Smooth steel samples were used to obtain data for the reference surface. The results showed that dimples promoted friction reduction (up to 20%) compared to the reference smooth specimens, whereas grooves generally caused less beneficial or detrimental effects. In addition, dimples promoted the formation of full film lubrication conditions at lower speeds. This study demonstrates how fast texturing techniques could potentially be used for improving the tribological performance of bearings as well as other mechanical components utilised in several engineering applications.

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A Simple Analysis of Texture-Induced Friction Reduction Based on Surface Roughness Ratio

Tribology Letters ◽

10.1007/s11249-021-01440-y ◽

2021 ◽

Vol 69 (2) ◽

Author(s):

Jiaxin Ye ◽

Jiazhou Xuan ◽

Yongliang Qiao ◽

Yifan Zhang ◽

Haiyang Zhang ◽

...

Keyword(s):

Surface Roughness ◽

Friction Reduction ◽

Simple Analysis

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Friction reduction by inlet temperature variation in microchannel flow

Physics of Fluids ◽

10.1063/5.0051998 ◽

2021 ◽

Vol 33 (6) ◽

pp. 062003

Author(s):

Dmitry S. Gluzdov ◽

Elizaveta Ya. Gatapova

Keyword(s):

Temperature Variation ◽

Friction Reduction ◽

Inlet Temperature ◽

Microchannel Flow

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Tribological Behaviour of Graphene Nanoplatelets as Additive in Pongamia Oil

Coatings ◽

10.3390/coatings11060732 ◽

2021 ◽

Vol 11 (6) ◽

pp. 732

Author(s):

Yeoh Jun Jie Jason ◽

Heoy Geok How ◽

Yew Heng Teoh ◽

Farooq Sher ◽

Hun Guan Chuah ◽

...

Keyword(s):

Friction And Wear ◽

Graphene Nanoplatelets ◽

Friction Reduction ◽

Engine Oil ◽

Protective Film ◽

Tribological Behaviour ◽

Wear Reduction ◽

Pongamia Oil ◽

Interacting Surfaces ◽

Worn Surface

This study investigated the tribological behaviour of Pongamia oil (PO) and 15W–40 mineral engine oil (MO) with and without the addition of graphene nanoplatelets (GNPs). The friction and wear characteristics were evaluated in four-ball anti-wear tests according to the ASTM D4172 standard. The morphology of worn surfaces and the lubrication mechanism of GNPs were investigated via SEM and EDS. This study also focuses on the tribological effect of GNP concentration at various concentrations. The addition of 0.05 wt % GNPs in PO and MO exhibits the lowest friction and wear with 17.5% and 12.24% friction reduction, respectively, and 11.96% and 5.14% wear reduction, respectively. Through SEM and EDS surface analysis, the surface enhancement on the worn surface by the polishing effect of GNPs was confirmed. The deposition of GNPs on the friction surface and the formation of a protective film prevent the interacting surfaces from rubbing, resulting in friction and wear reduction.

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