The Friction Reducing Effect of Square-Shaped Surface Textures under Lubricated Line-Contacts—An Experimental Study

Lu, Ping; Wood, R.J.K.; Gee, M.G.; Wang, Ling; Pfleging, Wilhelm

doi:10.3390/lubricants4030026

Cited by 42 publications

(27 citation statements)

References 23 publications

(23 reference statements)

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“…They suggested that this local friction response presumably is caused by the abrupt increase in film thickness. While similar local friction effects were observed in previous work by the current authors [47], that the friction drops as soon as the dimple array enters the contact area, and upward steps at trailing edge cause a friction increase. It should be noted that, in Vladescu's study, the relatively narrow and long rectangular pockets were fully covered in the contact area while sliding, whereas the previous work by the current authors was conducted with uncapped square dimples.…”

Section: Introductionsupporting

confidence: 90%

The use of anisotropic texturing for control of directional friction

Lu¹,

Wood²,

Gee

et al. 2017

Tribology International

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This paper presents a study on the influence of anisotropically shaped texture arrays on friction behaviour of an oil lubricated sliding contact, especially on directional friction control based on the diverging and converging characteristics of the textures. Experiments have been conducted on a TE77 reciprocating cylinder-on-plate test rig, where steel rollers were used to slide against steel plate samples with or without textures. A mineral base oil was used to lubricate the contacts. Three geometries of dimples were designed and laser textured on the steel plate samples with varied 3-dimensional features, including Square Flat (SF), Square slope (SS) and Triangular Flat (TF) shapes representing the shape in x-y (top view) and x-z (side view) planes respectively. These shapes were chosen to vary the converging and diverging properties of the lubricated contacts depending on the sliding direction. Relatively large dimple sizes (side length ~ and depth ~ ) have been used in this study to enable observation of the effect and easy control of the texturing process. The texture density has been kept at as most literature suggested. The large dimple sizes resulted that the dimples were not be fully covered by the contact area, i.e. the dimple sides were bigger than the Hertzian contact width of the roller-flat contacts. This has eliminated the 'lift' or 'load bearing' effect discussed in most papers thus focuses on other effects investigated in this study. The results show that beneficial effects of the anisotropic textures present in all lubrication regimes including the boundary, mixed and hydrodynamic lubrications, especially under prevailing boundary lubrication conditions. Using high sampling rate for the friction data during the tests, it was able to study local friction effect due to individual dimple array especially at their leading and trailing edges. The results show that a local friction reduction is observed at the leading while an increase at the trailing edge. Overall directional friction effect of the anisotropic textures has been observed that the converging shape in both y-z plane and the x-y plane reduces friction. Furthermore, it was found that the triangular shape dimples have a greater local frictional response at each dimple array, while the sloped bottom square dimples have a more significant overall directional fricition effect.

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Section: Introductionsupporting

confidence: 90%

The use of anisotropic texturing for control of directional friction

Lu¹,

Wood²,

Gee

et al. 2017

Tribology International

Self Cite

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“…5. The non-textured results are adapted from a paper published by the current authors [33]. As shown in Fig.…”

Section: Friction Resultsmentioning

confidence: 99%

“…As has been discussed in papers published by current authors [32,33], dimples parameters (dimple depth, dimple diameter, depth-to-diameter ratio, and the texture density, dimple profiles (flat, spherical and linearly varying bottoms) and dimple shapes (circular, elliptical, rectangular, triangular and chevron shapes) have been studied in the past decades. Researchers have been aware of the benefit of anisotropically textured surfaces through numerical simulation, that the converging shape in the x-y plane (triangular dimples) and in the x-z plane (sloped bottom dimples) could both be reasons for enhancing the lubrication effects [34,35].…”

Section: Introductionmentioning

confidence: 99%

“…The current research is a follow-up of a recently published work [32,33], aims at gaining a better understanding of the mechanisms that friction reduction effects and directional effects produced by dimpled surfaces at reciprocating speeds of the lubricated line contacts. To show whether these factors cause a significant impact, three samples with novel textured designs (triangular top-view shapes and wedge bottom shapes) were created by ultrafast laser surface texturing technique.…”

Section: Introductionmentioning

confidence: 99%

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A Novel Surface Texture Shape for Directional Friction Control

Lu¹,

Wood²,

Gee

et al. 2018

Tribol Lett

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An experimental study is presented to evaluate the influence of anisotropically shaped textures on the behaviour of sliding friction and sensitivity to sliding direction. The plate samples were textured with triangular sloped dimples using an ultrafast laser surface texturing technique. Reciprocating cylinder-on-plate tests were conducted with steel sliding pairs using mineral base oil as a lubricant to compare the tribological performance of reference non-textured specimen and dimpled samples. The dimples were designed with varying converging angles in the transverse y-z plane and top-view x-y plane. In this study, no dimple was fully covered in the contact area since the dimples size is much larger than the Hertzian line contact width. Stribeck style dynamic friction curves across boundary, mixed and hydrodynamic lubrication regimes were used to determine the benefit or antagonism of texturing. Observation of the directional friction effect of the anisotropic textures indicated that the converging shapes are beneficial for friction reduction, and the dimpled specimens have a lower friction coefficient particular under prevailing boundary lubrication conditions. It was also found that the real contact length variation rate is a major factor controlling the local friction response. The sloped bottoms of the textures produce effective converging wedge action to generate hydrodynamic pressure and contribute to the overall directional friction effects.

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“…However, few studies have looked at these two effects simultaneously (i.e. either surface topography's effect on oil consumption [4,5] or friction [6][7][8][9][10][11] have been studied). Their simultaneous investigation is necessary, since they are clearly interlinked.…”

Section: Piston Ring-liner Lubricationmentioning

confidence: 99%