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  • 51.
    Vrček, Aleks
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hultqvist, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Baubet, Yannick
    SKF, Nieuwegein.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 129, p. 338-346Article in journal (Refereed)
    Abstract [en]

    Current state-of-the-art engine oils tend to enhance micro-pitting damage in rolling contacts under certain operating conditions. ZDDP anti-wear additive was shown to promote such behavior. However, in order to optimize an engine oil formulation for rolling contacts, further studies are needed to assess engine oils in terms of micro-pitting and wear damage. This investigation studies the micro-pitting and wear performance of a number of engine oils for rolling contacts in a ball-on-disc configuration under conditions prevalent in crankshaft roller bearing applications. Based on the results it was concluded that an engine oil containing higher blend of PAO base oil compared to the oil mixture of Group III and PAO has a lower tendency towards micro-pitting and wear.

  • 52.
    Vrček, Aleks
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hultqvist, Tobias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Baubet, Yannick
    SKF Engineering & Research Centre, Nieuwegein, The Netherlands.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction2019In: Lubricants, E-ISSN 2075-4442, Vol. 7, no 5, article id 42Article in journal (Refereed)
    Abstract [en]

    Under certain operating conditions, rolling contacts have been shown to experience some challenges when lubricated with engine oils containing zinc dialkyldithophosphate (ZDDP) anti-wear additive. In order to better understand the main damage mechanisms during various operating conditions, further studies are needed. This article studies micro-pitting and wear damages of bearing steel surfaces under mixed lubrication conditions in a ball-on-disc setup, lubricated with different engine oils. Based on the results, micro-pitting and wear damage is shown to be highly case-dependent. In general, PAO-based engine oil tends to eliminate micro-pitting damage compared to mineral-based engine oil at less severe lubricating conditions. Moreover, a critical lambda was found for both oils, where the highest micro-pitting damage was observed. 

  • 53.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Application of an inclined, spinning ball-on-rotating disc apparatus to simulate railway wheel and rail contact problems2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 374-375, p. 46-53Article in journal (Refereed)
    Abstract [en]

    Railway wheel-rail contacts involve various combinations of slip, rolling, and creepage. Traditionally, a twin-disc apparatus is used to simulate such problems. However, there are out of plane forces and motions involved in the actual situation. Therefore, the possibility of using a commercially-made, inclined-axis spinning ball-on-disc test rig was investigated to better simulate wheel and rail contact problems. By setting two angle parameters both the lateral and spin creepage can easily be applied to the contact. Traction measurements were conducted, and good agreement was found by comparing the present results with other available experimental data. The effects of the spin creepage on wear were studied in particular. An asymmetrical wear pattern was obtained from cases that applied a low longitudinal creepage and a spin creepage, corresponding to a rail running on a curved track. To the best of the authors' knowledge, this work is the first of its kind to be done using a laboratory-scale tribometer.

  • 54.
    Xi, Yinhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Traction formula for rolling-sliding contacts in consideration of roughness under low slide to roll ratios2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 104, p. 263-271Article in journal (Refereed)
    Abstract [en]

    Based on the numerical results of a wide range of parameters in terms of the linear complementarity framework, an easy-to-use formula is presented by using the regression analyses to estimate the traction coefficient for rolling-sliding contacts under low Slide-to-Roll Ratio (SRR) domain for dry condition. The parameters include geometry, surface roughness, SRR and friction coefficient and contact radius. The formula's predictions are in good agreement with measurements using a ball on disc test rig. The results indicate that for steel-steel contact, the effects of third body layer and plasticity on the traction can almost cancel each other out. In addition, by revising the expression proposed by Masjedi and Khonsari, the formula is extended to estimate the cases under mixed lubrication.

  • 55.
    Zhang, Chen Hui
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Zhao, Ying Chun
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wang, Yan
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Lou, Jian Bin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    EHL properties of polyalkylene glycols and their aqueous solutions2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 45, no 3, p. 379-385Article in journal (Refereed)
    Abstract [en]

    Polyalkylene glycols (PAGs) are a type of synthetic lubricants widely used as compressor lubricants, gear oils, hydraulic fluids, and metal working fluids. The PAGs with typical molecular structure can dissolve in water, which makes it a candidate for the base stock of water-based lubricants. Till now, most of the investigations on the water-based lubrication have focussed on the additives. In this work, the potential of PAGs aqueous solutions to replace water as base stocks has been investigated. Four types of PAGs with different molecular weight and their aqueous solutions with different concentrations were studied to reveal their elastohydrodynamic lubrication (EHL) behavior. It has been found that the PAGs solutions can form EHL film like traditional oils. The film-forming capability depends on the viscosity, the pressure-viscosity coefficient, and the molecular weight of PAGs. The results indicate that the PAGs aqueous solution can be employed as base stocks of water-based lubricant

  • 56.
    Zhang, Chenhui
    et al.
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Zhao, Yingchun
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Luo, Jianbin
    State Key Laboratory of Tribology, Tsinghua University, Beijing.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Film forming characteristics of polyalkylene glycols aqueous solutions in EHL contact2011In: 6th China International Symposium on Tribology: August 19-22, 2011, Lanzhou, China, Lanzhou, China: State Key Laboratory of Solid Lubrication , 2011, p. 121-121Conference paper (Refereed)
12 51 - 56 of 56
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