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Lubricants, Volume 5, Issue 1 (March 2017)

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Editorial

Jump to: Research, Review

Open AccessEditorial Editorial: Friction and Lubricants Related to Human Bodies
Lubricants 2017, 5(1), 4; doi:10.3390/lubricants5010004
Received: 4 February 2017 / Revised: 4 February 2017 / Accepted: 4 February 2017 / Published: 13 February 2017
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(This article belongs to the Special Issue Friction and Lubricants Related to Human Bodies)
Open AccessEditorial Acknowledgement to Reviewers of Lubricants in 2016
Lubricants 2017, 5(1), 2; doi:10.3390/lubricants5010002
Received: 10 January 2017 / Revised: 10 January 2017 / Accepted: 10 January 2017 / Published: 10 January 2017
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Abstract The editors of Lubricants would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle The Effect of Non-Circular Bearing Shapes in Hydrodynamic Journal Bearings on the Vibration Behavior of Turbocharger Structures
Lubricants 2017, 5(1), 6; doi:10.3390/lubricants5010006
Received: 27 January 2017 / Revised: 24 February 2017 / Accepted: 26 February 2017 / Published: 3 March 2017
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Abstract
Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (sub)components mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic
[...] Read more.
Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (sub)components mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic bearings such as floating bearing rings. Particularly, the study of self-excited non-linear vibrations of the rotor-bearing systems is crucial for the understanding, prevention or reduction of the noise and, consequently, for a sustainable engine acoustics development. This work presents an efficient modeling approach for the investigation, optimization, and design improvement of complex turbocharger rotors in hydrodynamic journal bearings, including floating bearing rings with circular and non-circular bearing geometries. The capability of tonal non-synchronous vibration prevention using non-circular bearing shapes is demonstrated with dynamic run-up simulations of the presented model. These findings and the performance of our model are compared and validated with results of a classical Laval/Jeffcott rotor-bearing model and a specific turbocharger model found in the literature. It is shown that the presented simulation method yields fast and accurate results and furthermore, that non-circular bearing shapes are an effective measure to reduce or even prevent self-excited tonal noise. Full article
(This article belongs to the Special Issue Bearings in Turbomachinery)
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Open AccessArticle Influence of Organo-Sulfur Compounds with Overbased Calcium Compounds on Lubrication in Cold Forming
Lubricants 2017, 5(1), 8; doi:10.3390/lubricants5010008
Received: 29 December 2016 / Revised: 27 January 2017 / Accepted: 7 March 2017 / Published: 16 March 2017
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Abstract
The authors analyzed the structures of sulfurized olefins using NMR spectroscopy and studied the effects of sulfur chain length and alkyl structure on the ironing performance. They found that branched chain olefins, which contain branched alkyl groups, show superior ironing performance to straight
[...] Read more.
The authors analyzed the structures of sulfurized olefins using NMR spectroscopy and studied the effects of sulfur chain length and alkyl structure on the ironing performance. They found that branched chain olefins, which contain branched alkyl groups, show superior ironing performance to straight chain olefins, provided that their carbon numbers are relatively low. When the sulfurized olefins were used in combination with overbased detergents (calcium sulfonate or salicylate), they showed a higher performance in ironing than with sulfurized olefins alone. It was also found that lubricating films consisting of both iron sulfide and calcium carbonate seem to improve ironing performance. Full article
(This article belongs to the Special Issue Tribology in Manufacturing Process)
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Open AccessArticle The Influence of Tool Texture on Friction and Lubrication in Strip Reduction Testing
Lubricants 2017, 5(1), 3; doi:10.3390/lubricants5010003
Received: 28 October 2016 / Revised: 7 December 2016 / Accepted: 4 January 2017 / Published: 17 January 2017
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Abstract
While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades, tool surface texturing is rather new. In the present paper, tool texturing is studied as a method to prevent galling. A strip reduction test was conducted
[...] Read more.
While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades, tool surface texturing is rather new. In the present paper, tool texturing is studied as a method to prevent galling. A strip reduction test was conducted with tools provided with shallow, longitudinal pockets oriented perpendicular to the sliding direction. The pockets had small angles to the workpiece surface and the distance between them were varied. The experiments reveal that the distance between pockets should be larger than the pocket width, thereby creating a topography similar to flat table mountains to avoid mechanical interlocking in the valleys; otherwise, an increase in drawing load and pick-up on the tools are observed. The textured tool surface lowers friction and improves lubrication performance, provided that the distance between pockets is 2–4 times larger than the pocket width. Larger drawing speed facilitates escape of the entrapped lubricant in the pockets. Testing with low-to-medium viscosity oils leads to a low sheet roughness on the plateaus, but also local workpiece material pick-up on the tool plateaus. Large lubricant viscosity results in higher sheet plateau roughness, but also prevents pick-up and galling. Full article
(This article belongs to the Special Issue Tribology in Manufacturing Process)
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Open AccessFeature PaperArticle Rotordynamic and Friction Loss Measurements on a High Speed Laval Rotor Supported by Floating Ring Bearings
Lubricants 2017, 5(1), 7; doi:10.3390/lubricants5010007
Received: 30 January 2017 / Revised: 22 February 2017 / Accepted: 6 March 2017 / Published: 15 March 2017
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Abstract
Floating ring bearings are the commonly used type of bearing for automotive turbochargers. The automotive industry continuously investigates how to reduce the bearing friction losses and how to create silent turbochargers. Many of these studies involve creating a numerical model of the rotor-bearing
[...] Read more.
Floating ring bearings are the commonly used type of bearing for automotive turbochargers. The automotive industry continuously investigates how to reduce the bearing friction losses and how to create silent turbochargers. Many of these studies involve creating a numerical model of the rotor-bearing system and performing validation on a test bench on which a turbocharger is driven by hot gases. This approach, however, involves many uncertainties which diminish the validity of the measurement results. In this study, we present a test setup in which these uncertainties are minimized. The measurement results show the behavior of the floating ring bearing as a function of oil feed pressure, oil feed temperature, rotor unbalance and bearing clearances. Next to an increased validity, the test setup provides measurement data with good repeatability and can therefore represent a case study which can be used for validation of rotor-bearing models. Full article
(This article belongs to the Special Issue Bearings in Turbomachinery)
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Open AccessArticle Surface Film Adsorption and Lubricity of Soybean Oil In-Water Emulsion and Triblock Copolymer Aqueous Solution: A Comparative Study
Lubricants 2017, 5(1), 1; doi:10.3390/lubricants5010001
Received: 21 July 2016 / Revised: 23 December 2016 / Accepted: 23 December 2016 / Published: 30 December 2016
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Abstract
This paper investigates the surface film adsorption and lubricity of two different types of potential environmentally friendly cold metal forming lubricants: soybean vegetable oil in water VO/W emulsions and triblock copolymer aqueous solutions. The lubricants have different visual appearance, surface film adsorption characteristic,
[...] Read more.
This paper investigates the surface film adsorption and lubricity of two different types of potential environmentally friendly cold metal forming lubricants: soybean vegetable oil in water VO/W emulsions and triblock copolymer aqueous solutions. The lubricants have different visual appearance, surface film adsorption characteristic, lubricity and surface cleaning behaviour. The effects of concentration, temperature and emulsification ultrasonic energy (for VO/W emulsion) are studied. The result shows that the soybean VO/W emulsions have stronger adsorption, superior lubricity and anti-wear property compared to the copolymer solutions. The effect of temperature is investigated at 30 °C and 65 °C which are below and above cloud point of the aqueous copolymer solutions. Both lubricants show improved friction and anti-wear property at 65 °C. However, tenacious residual film remained on the discs surface after surface cleaning indicates lower cleanability of the soybean VO/W emulsions compared to the copolymer solutions, postulating the need for extra post-processing cleaning operations after cold forming process with VO/W emulsion lubricant. Full article
(This article belongs to the Special Issue Green Tribology)
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Review

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Open AccessReview Progress in Tribological Properties of Nano-Composite Hard Coatings under Water Lubrication
Lubricants 2017, 5(1), 5; doi:10.3390/lubricants5010005
Received: 28 June 2016 / Accepted: 14 February 2017 / Published: 17 February 2017
Cited by 2 | PDF Full-text (1592 KB) | HTML Full-text | XML Full-text
Abstract
The tribological properties, under water-lubricated conditions, of three major nano-composite coatings, i.e., diamond-like carbon (DLC or a-C), amorphous carbon nitride (a-CNx) and transition metallic nitride-based (TiN-based, CrN-based), coatings are reviewed. The influences of microstructure (composition and architecture) and test conditions (counterparts and friction
[...] Read more.
The tribological properties, under water-lubricated conditions, of three major nano-composite coatings, i.e., diamond-like carbon (DLC or a-C), amorphous carbon nitride (a-CNx) and transition metallic nitride-based (TiN-based, CrN-based), coatings are reviewed. The influences of microstructure (composition and architecture) and test conditions (counterparts and friction parameters) on their friction and wear behavior under water lubrication are systematically elucidated. In general, DLC and a-CNx coatings exhibit superior tribological performance under water lubrication due to the formation of the hydrophilic group and the lubricating layer with low shear strength, respectively. In contrast, TiN-based and CrN-based coatings present relatively poor tribological performance in pure water, but are expected to present promising applications in sea water because of their good corrosion resistance. No matter what kind of coatings, an appropriate selection of counterpart materials would make their water-lubricated tribological properties more prominent. Currently, Si-based materials are deemed as beneficial counterparts under water lubrication due to the formation of silica gel originating from the hydration of Si. In the meantime, the tribological properties of nano-composite coatings in water could be enhanced at appropriate normal load and sliding velocity due to mixed or hydrodynamic lubrication. At the end of this article, the main research that is now being developed concerning the development of nano-composite coatings under water lubrication is described synthetically. Full article
(This article belongs to the Special Issue Green Tribology)
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