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Textured surfaces for improved lubrication at high pressure and low sliding speed of roller/piston in hydraulic motors
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
2007 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, no 2, 355-359 p.Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

The present study investigates the potential of surface textures to improve the friction situation of the piston/roller contact in hydraulic motors at low speed and high pressure. A self-adjusting flat on flat rig, with conditions representative of an actual hydraulic motor, is used in a reciprocating sliding motion. The samples are made out of the same materials and the surface finishing operations are the same as used in the motor.

The piston surfaces are textured using newly developed embossing tools comprising micromechanically formed all-diamond surfaces. The textured surfaces involve parallel grooves and crossed grooves, each of four different spacings. Also polished surfaces were tested. Un-textured—as tumbled—surfaces are used as reference.

Generally, it was found that the friction level was only marginally influenced by the textures. However, the friction fluctuations were reduced. SEM investigations disclosed rather severe modifications of the surfaces during use, primarily caused by plastic deformation of the surface layer. The results and their practical implications are discussed.

Place, publisher, year, edition, pages
2007. Vol. 40, no 2, 355-359 p.
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-93178DOI: 10.1016/j.triboint.2005.11.024ISI: 000242317900028OAI: oai:DiVA.org:uu-93178DiVA: diva2:166575
First International Conference on Advanced Tribology (iCAT 2004), Singapore
Available from: 2005-05-17 Created: 2005-05-17 Last updated: 2016-04-07Bibliographically approved
In thesis
1. Surfaces Designed for High and Low Friction
Open this publication in new window or tab >>Surfaces Designed for High and Low Friction
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Ytor utformade för hög och låg friktion
Abstract [en]

This thesis comprises tribological studies of extremely well-defined surfaces of different designs. Both low-friction and high-friction surfaces were manufactured and experimentally evaluated.

In the low-friction studies, lithography and anisotropic etching of silicon was first used as a texturing technique. The textured surfaces were subsequently PVD coated with TiN or DLC to achieve tribologically relevant interfaces. The results showed that under starved lubricated conditions, fine surface textures lowered the coefficient of friction and the wear rate. It was shown that also the orientation of the texture is of major importance for the lubricating function.

Further, a novel embossing technique was developed, permitting texturing of steel and other materials. A micro mechanically designed diamond tool was used to emboss steel surfaces. The roller/piston contact from a hydraulic motor was simulated and introduction of an embossed texture on the piston decreased the level and the fluctuation of the friction. The effect of the texture was here similar to the effect of an additional polish step. However, in general it is not an easy task to substantially improve a boundary lubricated contact by introducing a texture.

Studies of high friction surfaces were performed on micro mechanically designed diamond surfaces equipped with sharp pyramids or ridges. Just as theory predicts, the coefficient of friction was dependent on the shape of the ploughing bodies, but not on the counter material or the load. The tested surfaces resulted in static coefficients of friction between 1.1 and 1.6, depending on surface design and orientation. These are extremely high values, and therefore very interesting for practical applications requiring a high static friction.

Conclusively, the present thesis shows that it is possible to design and produce surfaces both for improved lubrication in sliding contact and for substantially improved high friction performance in static contacts.

Place, publisher, year, edition, pages
Uppsala: Institutionen för teknikvetenskaper, 2005. 43 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 63
Materials science, tribology, friction, surface texture, surface design, low friction, high friction, boundary lubrication, DLC, embossing, Materialvetenskap
National Category
Materials Engineering
urn:nbn:se:uu:diva-5835 (URN)91-554-6278-2 (ISBN)
Public defence
2005-06-07, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Available from: 2005-05-17 Created: 2005-05-17Bibliographically approved

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