High‐speed optical imaging of liquid film flow and liquid macro‐slip over free surfaces with different surface energies

Published on Dec 1, 2017in Lubrication Science1.985
· DOI :10.1002/LS.1388
M. Polajnar5
Estimated H-index: 5
(University of Ljubljana),
Benjamin Bizjan8
Estimated H-index: 8
(University of Ljubljana)
+ 1 AuthorsMitjan Kalin40
Estimated H-index: 40
(University of Ljubljana)
Source
Abstract
High-speed optical imaging is introduced as a visualization method to investigate the film-flow properties of liquids with different surface tensions and viscosities (water, poly-alpha-olefin oil, and glycerol) over free rotating surfaces with different surface energies and polarities (steel, and two different diamond-like-carbon - DLC coatings, i.e. DLC, and F-DLC). It was found that the polar surface energy strongly influences the structural dynamics of the liquid film's flow and the film's slip. Namely, a decrease in the polar surface energy results in a less stable film with de-wetting areas and breakups into streams, as well as in a larger amount of film slip, which was most clearly expressed by the F-DLC. It was also found that the combination of a high surface tension and a low viscosity provides the largest amount of liquid slip, with the most obvious breakup of the liquid film being observed with water, which clearly exhibits these properties.
📖 Papers frequently viewed together
4 Authors (Xiaoyu Tang, ..., Chao Sun)
References43
Newest
#1Lars Bobach (Otto-von-Guericke University Magdeburg)H-Index: 6
#2Dirk Bartel (Otto-von-Guericke University Magdeburg)H-Index: 13
Last. Holger Ziegele (BMW)H-Index: 4
view all 9 authors...
This work evaluates the influence of DLC coatings on the frictional behaviour of lubricated line contacts in the fluid friction regime. Experiments on a twin-disc machine showed a significant reduction in friction using DLC coated discs instead of uncoated ones. The experimental results are compared by calculations using a three-dimensional thermal elastohydrodynamic simulation model. According to the calculations, the lower heat conductivity of DLC coatings is the main reason for the reduction ...
Source
#1M. Polajnar (University of Ljubljana)H-Index: 5
#2Mitjan Kalin (University of Ljubljana)H-Index: 40
In this paper, we show how the slide-to-roll ratio (SRR), the contact kinematics and the surface energy all have important effects on the elastohydrodynamic friction. As reported previously, diamond-like-carbon (DLC) contacts of the type DLC/DLC provide the lowest coefficient of friction, in particular those DLC materials with the lowest surface energies (three different DLC coatings were used in this study). A friction reduction of up to 48 %, compared to a steel/steel contact, was obtained. A ...
Source
#1L. Guo (CityU: City University of Hong Kong)H-Index: 7
#2P.L. Wong (CityU: City University of Hong Kong)H-Index: 20
Last. F. Guo (QUT: Qingdao Technological University)H-Index: 9
view all 3 authors...
The strength of molecular adhesion at the lubricant–solid interface plays a key role in determining the load-carrying and film forming capacity of a lubricated system of meso- or microscale. If the liquid molecules gain higher energies than the potential energy barrier for adhesion, slip occurs at the interface. The contact angle of a liquid on a solid surface is related to the intermolecular attractive force. Some studies demonstrated the connection of the contact angle to the lubrication effec...
Source
#1Jian-Yi Wang (CAS: Chinese Academy of Sciences)H-Index: 4
#2Yu Shan (CAS: Chinese Academy of Sciences)H-Index: 8
Last. Junhong Jia (CAS: Chinese Academy of Sciences)H-Index: 24
view all 6 authors...
Ni-based composite that contains TiO2 and Al2O3 was prepared by powder metallurgical hot pressing method. TiO2 and Al2O3 being added to Ni-based composite at the same mass fraction and the effects on some mechanical and tribological properties of the composites when rubbing against alumina ball were investigated from room temperature to 700 °C. The results show that the tribological properties of the composites were improved by adding TiO2 and Al2O3 simultaneously. The best comprehensive propert...
Source
#1Z. Fu (SZU: Shenzhen University)H-Index: 1
#2P.L. Wong (CityU: City University of Hong Kong)H-Index: 20
Last. F. Guo (QUT: Qingdao Technological University)H-Index: 9
view all 3 authors...
The study aimed to determine the formation of an adsorption film at elastohydrodynamic lubricated (EHL) contacts and its effects on EHL film shape and friction. Experiments were conducted on an optical EHL test rig with surfaces of different surface energies. A new type of “abnormal” EHL film shape characterized with three dimples in the inlet of the contact was obtained in pure ball sliding experiments with long-chain polybutene. The adsorption layer was inferred to be the main cause for the “t...
Source
#1Benjamin Bizjan (University of Ljubljana)H-Index: 8
#2Brane Širok (University of Ljubljana)H-Index: 21
Last. Alen OrbanićH-Index: 9
view all 4 authors...
Abstract In this paper, liquid disintegration by a spinning wheel was investigated experimentally. The mechanism of ligament formation on a spinning wheel was studied using photographs taken by a high-speed camera. Three different liquids with Newtonian properties were used at various flow rates and the wheel rotational speed was varied in a wide range. The atomization process was found to be significantly different from the spinning disc and cups atomization due to the highly non-uniform circum...
Source
#1Marcus Björling (Luleå University of Technology)H-Index: 14
#2Roland Larsson (Luleå University of Technology)H-Index: 30
Last. Pär Marklund (Luleå University of Technology)H-Index: 14
view all 3 authors...
The application of surface coatings has been shown to reduce friction in elastohydrodynamic lubrication (EHL), not only in the mixed and boundary regime when asperity interactions occur, but also in the full film regime. Several studies suggest that the full film friction reduction is due to a violation of the no-slip boundary condition and thus slip is taking place between the solid and the liquid. Another hypothesis proposes that the full film friction reduction is due to the low thermal condu...
Source
#1Aleks Ponjavic (Imperial College London)H-Index: 13
#2Janet S. S. Wong (Imperial College London)H-Index: 16
The effect of interfacial slip on the friction and film thickness in an elastohydrodynamic (EHD) contact was directly evaluated. Experiments showed that the film thickness and friction decrease upon the application of an oleophobic coating given a sufficient pressure, as opposed to bare glass. Direct measurements of the slip velocity enabled the determination of a power law relationship between pressure and slip length. This implied the existence of spatial heterogeneity of the flow in the tribo...
Source
#2F. Ch. Birjandi (IAU: Islamic Azad University)H-Index: 2
#3Javad Sargolzaei (FUM: Ferdowsi University of Mashhad)H-Index: 16
Abstract The liquid repellency is one of the crucial surface properties which plays important roles in many practical applications but the researches related to this field are in their infancy. This article reviews the fundamental theories and recent achievements in the design, fabrication and applications of super-non-wettable surfaces.
Source
#1Mitjan Kalin (University of Ljubljana)H-Index: 40
#2M. Polajnar (University of Ljubljana)H-Index: 5
Abstract The importance of wetting is becoming increasingly obvious and its control is inevitable in many engineering applications, including tribology and interface nanotechnology. However, the relations between the key parameters affecting surface–liquid wetting behaviour under realistic conditions are not very well understood, especially for typical engineering materials and lubricants (oils), often leading to exceptions and contradictions, which impede their use in engineering models and the...
Source
Cited By1
Newest
#1Benjamin Bizjan (University of Ljubljana)H-Index: 8
#2Brane Širok (University of Ljubljana)H-Index: 21
Last. Marko Blagojevič (University of Ljubljana)H-Index: 1
view all 3 authors...
Source
This website uses cookies.
We use cookies to improve your online experience. By continuing to use our website we assume you agree to the placement of these cookies.
To learn more, you can find in our Privacy Policy.