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  • 101. Waara, Patric
    et al.
    Hannu, Jesper
    Luleå University of Technology.
    Norrby, Thomas
    Byheden, Åke
    Additive influence on wear and friction performance of environmentally adapted lubricants2001In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, no 8, p. 547-556Article in journal (Refereed)
    Abstract [en]

    In this paper, the influence of concentration level and chemical composition of three different additive types on friction and wear coefficient are presented for a synthetic ester base fluid and a mineral base oil. One extreme-pressure (EP), two antiwear (AW) and two yellow metal passivator (Cu-passivators) additives were used. Factorial experimental design was used as the basis for a systematic evaluation of wear rates under mixed and boundary lubrication conditions. A total of 33 different lubricant blends were tested in a Plint and Partner High Frequency Friction Machine. For the synthetic ester, the extreme-pressure (EP) additive, containing phosphorus and nitrogen, was found to be much more effective in reducing wear than either of the two antiwear (AW) additives tested. In fact, the AW and Cu-passivator additives made little or no contribution to the wear protection in most of the cases studied. A synergy effect between the three additive combinations was observed only for the reference mineral oil blend. A significant difference between the antiwear performance of the test lubricants was found. This study suggests that the traditional "AW" and "EP" labels associated with commonly used additives are poor aids when designing of ester based lubricants.

  • 102.
    Wu, Jian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing University of Chemical Technology, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Halogen-free ionic liquids as excellent lubricants for PEEK-stainless steel contacts at elevated temperatures2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 104, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Advanced polymers sliding against steel under ionic liquids (ILs) has great potential applications. However, halogen-containing ILs (h-ILs) often induce high corrosive wear to steel. In this work, halogen-free ILs (hf-ILs) were used as neat lubricants to investigate the performance of poly(ether-ether-ketone)-AISI304 stainless steel (PEEK-304ss) contacts at elevated temperatures. The results indicate that hf-ILs with short alkyl chains show excellent anti-corrosion and antiwear properties. The wear rates of 304ss lubricated by hf-ILs at 160 °C are 3–71% of those by h-ILs. The friction coefficients of PEEK-304ss lubricated by hf-ILs are just 13–33% of those by h-ILs. The excellent performance of hf-ILs can be attributed to the reason that hf-ILs will not generate any halogen containing acid during the test

  • 103.
    Wu, Jian
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211800, China.
    Luo, Yanlong
    College of Science, Nanjing Forestry University, Nanjing 210037, China.
    Chen, Yifeng
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211800, China.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211800, China.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211800, China.
    Bao, Ningzhong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211800, China.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Poly(ionic liquid)s as lubricant additives with insight into adsorption-lubrication relationship2022In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 165, article id 107278Article in journal (Refereed)
    Abstract [en]

    Ionic liquids (ILs) are very potential lubricant additives for their strong adsorption and tribochemical reactions at the interface. In this work, poly(ionic liquid) of PImC6NTf2 is used as lubricant additive in base oil of PEG, which can reduce the wear volume by around 65 times under 2.5 GPa. The lubricity is much more advantageous than the geminal dicationic IL of BIm5-(NTf2)2. The adsorption strength of lubricants is studied by employing the microcalorimeter to evaluate the adsorption heat, AFM to test the adhesion force, and molecular dynamics simulation to calculate the interfacial binding energy. As a result, the adsorption strength of PImC6NTf2 is obviously higher than BIm5-(NTf2)2, and the lubricity is strongly dependent on the adsorption strength of ILs.

  • 104.
    Wu, Jian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Mu, Liwen
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Chen, Yifeng
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Yin, Xiang
    State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Larsson, Roland
    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.
    Turning the solubility and lubricity of ionic liquids by absorbing CO22018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 121, p. 223-230Article in journal (Refereed)
    Abstract [en]

    Ionic liquids (ILs) attract high interest as lubricants or lubricant additives due to their special physicochemical characteristics. CO2 is a widely distributed gas. In many situations, its influence on lubricants cannot be avoided. In this work, three ILs are synthesized from choline and amino acids of glycine, l-proline and lysine, respectively. The influence of CO2 absorption on their solubility and lubricity is investigated. In general, it is interesting to find that the solubility is decreased and their lubricity is obviously improved after absorbing CO2, which is strongly related to their functional group (amino group) interactions with CO2. The formation of carbamate groups greatly increases the viscosity resulting in less solid contacts, and strengthens the interfacial adhesion between ILs and solids.

  • 105.
    Wu, Jian
    et al.
    State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, PR China.
    Zhu, Jiahua
    Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325, USA.
    Mu, Liwen
    School of Materials Engineering, Nanjing Institute of Technology, Nanjing 211167, PR China.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Dong, Yihui
    State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, PR China.
    Feng, Xin
    State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, PR China.
    Lu, Xiaohua
    State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, PR China.
    High load capacity with Ionic liquid-lubricated tribological system2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 94, p. 315-322Article in journal (Refereed)
    Abstract [en]

    Engineering polymers with high glass transition temperature have been widely used in dynamic friction systems by oil or solid lubrication. However, in high-load systems, oil lubrication is less efficient due to the viscosity decrease at higher temperatures induced by friction heat. [Bmim][PF6] ionic liquid was used and compared with traditional L-HM46 oil and solid PTFE. Taking advantage of high [Bmim][PF6] viscosity, strong steel-[Bmim][PF6] but poor PEEK-[Bmim][PF6] interaction, the [Bmim][PF6] lubricated PEEK/steel slide falls in hydrodynamic lubrication and elastohydrodynamic lubrication region under 150–1500 N. While the oil and PTFE both failed to lubricate under 800 N.

  • 106.
    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.

  • 107.
    Yu, Qiangliang
    et al.
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Zhang, Chaoyang
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Dong, Rui
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; University of Chinese Academy of Sciences, Beijing, China.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wang, Yurong
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; University of Chinese Academy of Sciences, Beijing, China.
    Bai, Yanyan
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; University of Chinese Academy of Sciences, Beijing, China.
    Zhang, Jiaying
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China; School of Materials Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China.
    Cai, Meirong
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Zhou, Feng
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China.
    Novel N, P-containing oil-soluble ionic liquids with excellent tribological and anti-corrosion performance2019In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 132, p. 118-129Article in journal (Refereed)
    Abstract [en]

    Two oil-soluble ionic liquids N, N-trimethyl-N-hexadecyl ammonium bis(2-ethylhexyl) phosphate (NP-16))and 1,2-bis-NN-dimethyl-N-cetylammonium bis (2-ethylhexyl) phosphate (NP-16-2-16) have been synthesized and investigated as a potential friction reduction and anti-wear lubricant additive with anti-corrosion properties. The results indicate that the addition of 1.0 wt % NP-16 into PAO10 can significantly reduce friction coefficient and improve its anti-wear performance under RT and 100 °C. The performance is obviously better than that of traditional additives ZDDP and tricresyl phosphate. PAO10 + 1.0 wt % NP-16 even outperformed the PAO10 with about 40% lower friction and 2 orders of magnitude less wear. The analysis results of SEM, EDS and XPS show that an FePO4 or nitrogen-containing tribofilm is formed on the friction interface when NP-16 and NP-16-2-16 are selected as additives, which play a key role in reducing friction and wear.

  • 108.
    Zapata Tamayo, Juan Guillermo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Royal Institute of Technology KTH, Department of Engineering Design, Stockholm 100 44, Sweden.
    Björling, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Division of Machine Elements, Department of Engineering Sciences and .
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    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.
    Micropitting performance and friction behaviour of DLC coated bearing steel surfaces : On the influence of Glycerol-based lubricants2024In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 196, article id 109674Article in journal (Refereed)
    Abstract [en]

    A better understanding about the rolling contact fatigue and micropitting performance of machine component surfaces lubricated with environmentally friendly lubricants is critical to designing and further formulating new lubricants intended to be used in rolling–sliding contacts such as those found in gear and bearing applications. In this work, the frictional behaviour and rolling contact fatigue (RCF) performance of DLC, Cr/a-WC:H/a-C:H and a-C:Cr coatings under glycerol-based lubrication in rolling sliding contact conditions have been investigated. Traction maps, Stribeck curves, and fatigue plots have been generated by using a micropitting test rig (MPR). The initiation and progression of micropitting was monitored by means of white light optical interferometry and scanning electron microscopy (SEM). Results indicated that glycerol-based lubricants exhibited a significant friction reduction as the hydrodynamic effect is enhanced at higher rolling-speeds. Under boundary lubrication the friction coefficient was significantly higher compared to the values obtained with a commercial mineral-based transmission oil. Compared to uncoated steel surfaces, DLC coatings effectively reduced the volume loss and micropitting progression. Irrespective of the coating thickness, DLC showed an excellent tribological behaviour when the base lubricant favours the onset of mild-wear, over micropitting. When the lubricant formulation favoured the onset of micropitting, the coatings tended to prematurely fail due to debonding from the substrate, and local micro-spallation. The experiments demonstrated that friction reduction does not necessarily correspond with a reduction of micropitting.

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  • 109.
    Åhrström, Bert-Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Investigation of frictional properties of lubricants at transient elastohydrodynamic conditions2001In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, no 12, p. 809-814Article in journal (Refereed)
    Abstract [en]

    In the assessment of lubricant properties and in various contact applications, it is of importance to know the frictional qualities. Under quasi-static conditions, normal and transverse forces are measured using force transducers but the task is more difficult when loads are high and transient, as they often are in elastohydrodynamic conjunctions. The experimental method presented in this paper is based on analysis of propagating waves in a beam, due to an impact on its end surface, using FFT analysis. Since the impact is oblique, both non-dispersive compression waves and dispersive flexural waves are generated. The normal force originating from the axial wave is measured using straingauges, while the transverse force is derived from the FFT's of two lateral acceleration histories using Euler-Bernoulli dynamic beam theory. The relation between normal- and transverse force histories displays the frictional properties at the impact as a function of time, i.e. variations in frictional properties during loading and unloading (typically 200-400 μs in ball bearings and gears) can be observed. A variety of lubricants have been studied up to a Hertzian pressure of 2.5 GPa, and the method and results are presented.

  • 110.
    Åström, Henrik
    et al.
    Luleå University of Technology.
    Isaksson, Ove
    Luleå University of Technology.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Video recordings of an EHD point contact lubricated with grease1991In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 24, no 3, p. 179-184Article in journal (Refereed)
    Abstract [en]

    Optical interferometry has been used to study the film thickness of an EHD point contact lubricated with grease. The greases used were two lithium, two lithium complex and two sodium greases, all with NLGI grade two, the most common grade. They were based on one mineral oil of naphthenic type and one synthetic polyalphaolefin. The contact was lubricated without a continuous supply of grease and thus the film thickness decreased with time as the grease was gradually squeezed away from the contact area. The film thickness fluctuated during the measurement. To overcome this problem, the contact point was recorded with a video camera and the results evaluated after the tests. The video camera proved to be a powerful help in this evaluation. The tests were run at 20°C and under pure rolling conditions at a rolling velocity of 0.055 m s-1. The results from all greases showed a decreasing film thickness that tended to stabilize on about 0.2 μm after 40 cycles. The lithium and lithium complex greases showed strong local film thickness variations inside the lubricated contact, deviating from the normally horseshoe-shaped contact, during the first 20 to 40 cycles.

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