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  • 1.
    Shu, Ju
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Harris, Kathryn
    KTH, School of Industrial Engineering and Management (ITM).
    Munavirov, B.
    Westbroek, R.
    Leckner, J.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM). Soete Laboratory, Ghent University, B-9000 Ghent, Belgium.
    Tribology of polypropylene and Li-complex greases with ZDDP and MoDTC additives2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 118, 189-195 p.Article in journal (Refereed)
    Abstract [en]

    The influence of thickener and additive interactions on grease lubricating performance is examined. Polypropylene and lithium complex thickened (Li-complex) greases were tested both as neat greases and with a 2 wt% addition of ZDDP and/or MoDTC. A combination of ZDDP and MoDTC in the polypropylene grease provided the lowest friction with greater longevity compared to the Li-complex grease with the same additives, independent of sliding speed, contact pressure, temperature or type of sliding: continuous vs. reciprocating. The additive combination of ZDDP and MoDTC provided the best antiwear performance in both greases. Depending on the grease sample type, EDS revealed the presence of iron, zinc, phosphorous, sulfur, and molybdenum within the tribofilms.

  • 2. Filippov, Andrei
    et al.
    Gnezdilov, Oleg I.
    Hjalmarsson, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Antzutkin, Oleg N.
    Glavatskih, Sergei
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Acceleration of diffusion in ethylammonium nitrate ionic liquid confined between parallel glass plates2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 38, 25853-25858 p.Article in journal (Refereed)
  • 3. Filippov, A.
    et al.
    Gnezdilov, O. I.
    Hjalmarsson, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Antzutkin, O. N.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM). Ghent University, Belgium.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. RISE Technical Research Institute of Sweden.
    Acceleration of diffusion in ethylammonium nitrate ionic liquid confined between parallel glass plates2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 38, 25853-25858 p.Article in journal (Refereed)
    Abstract [en]

    Diffusion of EAN confined between polar glass plates separated by a few micrometers is higher by a factor of ca. 2 as compared to bulk values. Formation of a new phase, different to the bulk, was suggested.

  • 4. Javed, Muhammad Asadullah
    et al.
    Ahola, Susanna
    Hakansson, Par
    Mankinen, Otto
    Aslam, Muhammad Kamran
    Filippov, Andrei
    Shah, Faiz Ullah
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Antzutkin, Oleg N.
    Telkki, Ville-Veikko
    Y Structure and dynamics elucidation of ionic liquids using multidimensional Laplace NMR2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 80, 11056-11059 p.Article in journal (Refereed)
  • 5.
    Wang, Yong-Lei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Shimpi, Manishkumar R.
    Sarman, Sten
    Antzutkin, Oleg N.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Univ Ghent, Belgium.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Laaksonen, Aatto
    Atomistic Insight into Tetraalkylphosphonium Bis(oxalato)borate Ionic Liquid/Water Mixtures. 2. Volumetric and Dynamic Properties2016In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, no 30, 7446-7455 p.Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics simulations have been performed to investigate volumetric quantities and dynamic properties of binary trihexyltetradecylphosphonium bis(oxalato)-borate ([P-6,P-6,P-6,P-14][BOB]) ionic liquid (IL)/water mixtures with different water concentrations. The predicted liquid densities for typical [P-6,P-6,P-6,P-14][BOB] IL/water mixtures are consistent with available experimental data with a relative discrepancy of less than 3%. The liquid densities and excess molar volumes of all studied [P-6,P-6,P-6,P-14][BOB] IL/water mixtures are characterized by concave and convex features, respectively, within full water concentration range. The dynamic properties of [P-6,P-6,P-6,P-14] cations, [BOB] anions, and water molecules are particularly analyzed through calculation of velocity autocorrelation functions, diffusion coefficients, and reorientational autocorrelation functions and correlation times. The translational and reorientational mobilities of three species become faster upon increasing water concentration in [P-6,P-6,P-6,P-14][BOB] IL/water mixtures and present complex dynamical characteristics arising from three distinct microscopic diffusion features within the full water concentration range. The obtained striking volumetric quantities and particular dynamic properties are well correlated to microscopic liquid structural organization and distinct local ionic environment of all studied [P-6,P-6,P-6,P-14][BOB] IL/water mixtures.

  • 6.
    Kuznetsov, Evgeny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). COMSOL LLC, Russian Federation.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Ghent University, Belgium .
    Dynamic characteristics of compliant journal bearings considering thermal effects2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 94, 288-305 p.Article in journal (Refereed)
    Abstract [en]

    A numerical THD model that takes into account mechanical and thermal deformations of a compliant lining is used to investigate the influence of compliance on dynamic characteristics of a two axial groove bearing. A detailed study on the contribution of mechanical and thermal deformation components of the compliant lining to the non-dimensional bearing stiffness and damping is carried out. Thermal deformation is found to increase horizontal stiffness K<inf>yy</inf> and cross-coupled stiffness K<inf>xy</inf> and slightly reduce journal critical mass. Mechanical deformation of the compliant lining is found to decrease damping, reduce vertical and cross-coupled K<inf>xy</inf> stiffness. Radial clearance is found to increase stiffness, except its horizontal component, and decrease horizontal damping. Compliant lining is found to improve bearing stability.

  • 7.
    Ploss, Moritz A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Influence of electric potential on the apparent viscosity of an ionic liquid: facts and artifacts2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 38, 26609-26615 p.Article in journal (Refereed)
    Abstract [en]

    According to recent findings, the steady shear viscosity of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([Emim][Tf2N]) decreases significantly under the influence of electric potential. This implies a causal connection between nanoscale ordering at the electrified interface and a macroscopic change of transport properties. To study this phenomenon in more detail, we reproduced the above-mentioned measurements; however, we find no evidence that the viscosity of [Emim][Tf2N] is a function of electric potential. Additionally, our results show that steady shear measurements can lead to artifacts that, at first glance, may appear to be potential-induced changes in viscosity. We demonstrate that the artifacts result from a sliding electrical contact at the working electrode of the electrochemical cell and we suggest to consider our findings for future viscosity measurements of ionic liquids.

  • 8. Filippov, Andrei
    et al.
    Azancheev, Nail
    Shah, Faiz Ullah
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM).
    Antzutkin, Oleg N.
    Self-diffusion of phosphonium Bis(Salicylato)Borate ionic liquid in pores of Vycor porous glass2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 230, 128-134 p.Article in journal (Refereed)
    Abstract [en]

    H-1 NMR pulsed field gradient was used to study self-diffusion of a phosphonium bis(salicylato)borate ionic liquid ([P6,6,6,14][BScB]) in the pores of Vycor porous glass at 296 K. Confinement in pores increases diffusion coefficients of the ions by a factor of 35. However, some [P6,6,634][BScB] ions demonstrated apparent diffusion coefficients much lower than their mean values, which may be due to partially restricted diffusion of the ions. We suggest that this fraction corresponds to areas where ions are confined by pore 'necks' (micropores) and empty voids. Heating of the ionic liquid/Vycor system at 330 K led to a change in the diffusivity of the ions, because of their redistribution in the pores. The size of the bounded regions is on the order of 1 mu m, as estimated from the dependence of the ion diffusivity on the diffusion time.

  • 9.
    Wang, Yong-Lei
    et al.
    KTH.
    Sarman, Sten
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Antzutkin, Oleg N.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Laaksonen, Aatto
    Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 6, 064507Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics simulations have been performed to investigate effective interactions of isolated water molecules dispersed in trihexyltetradecylphosphonium-orthoborate ionic liquids (ILs). The intrinsic free energy changes in solvating one water molecule from gas phase into bulk IL matrices were estimated as a function of temperature, and thereafter, the calculations of potential of mean force between two dispersed water molecules within different IL matrices were performed using umbrella sampling simulations. The systematic analyses of local ionic microstructures, orientational preferences, probability and spatial distributions of dispersed water molecules around neighboring ionic species indicate their preferential coordinations to central polar segments in orthoborate anions. The effective interactions between two dispersed water molecules are partially or totally screened as their separation distance increases due to interference of ionic species in between. These computational results connect microscopic anionic structures with macroscopically and experimentally observed difficulty in completely removing water from synthesized IL samples and suggest that the introduction of hydrophobic groups to central polar segments and the formation of conjugated ionic structures in orthoborate anions can effectively reduce residual water content in the corresponding IL samples.

  • 10. Wang, Y. -L
    et al.
    Sarman, S.
    Glavatskih, Sergei B.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Antzutkin, O. N.
    Rutland, M. W.
    Laaksonen, A.
    Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures. I. Local microscopic structure2015In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 119, no 16, 5251-5264 p.Article in journal (Refereed)
    Abstract [en]

    Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P<inf>6,6,6,14</inf>][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P<inf>6,6,6,14</inf>] cations and isolated polar domains consisting of the central segments of [P<inf>6,6,6,14</inf>] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P<inf>6,6,6,14</inf>] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P<inf>6,6,6,14</inf>][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P<inf>6,6,6,14</inf>] cations. © 2015 American Chemical Society.

  • 11.
    Cha, Matthew
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Dynamic Performance and Design Aspects of Compliant Fluid Film Bearings2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to government regulations together with health and safety reasons, there are increasing demands on reducing hazardous polluting chemicals from fossil fuel power plants. Therefore, more efforts are imposed on using renewable resources such as water, wind, solar and tide to produce clean/green electricity. On top of that, there is another increasing demand from Original Equipment Manufacturers (OEMs) to operate power plants with higher load while keep the power loss to the minimum. These requirements drive conventional fluid film bearings to its mechanical and temperature limits. This calls for the development of new bearing system designs. An outstanding tribological performance such as low start-up and break-away friction, excellent resistance to chemical attack and anti-seizure properties, can be achieved by introducing compliant polymer liners. At the same time, bearings with compliant liners may alter rotor-bearing system dynamic behaviour compared to the systems with conventional white metal bearings. The research approach of this thesis is to implement compliant liner on bearing surface, impose synchronous shaft excitation and investigate the effect of bearing design parameters on bearing dynamic response.

    Plain cylindrical journal bearings with different compliant liner thicknesses were analysed using a FEM approach. The numerical model was compared with an in-house developed code based on the finite difference method (FDM) for a bearing operated at steady state conditions. Results obtained by the numerical models showed good agreement. After verification of the numerical model for fixed geometry journal bearings, models for tilting pad journal bearings were developed. Dynamic behaviour of the tilting pad journal bearing with three pads with line pivot geometry was compared with published data. A good agreement was obtained between the two numerical models. The effect of pad pivot geometry on bearing dynamic response was investigated. Vertical and horizontal shaft configurations were compared in terms of the effect of preload factor, radial clearance, pivot offset, and pad inclination angles. Influence of the elastic properties of compliant liners was also studied. All these factors significantly affect bearing dynamic response. It is shown how these factors should be selected to control the journal orbit sizes. Misalignments in compliant tilting pad journal bearings were analysed for load between pivots and load on pivots with consideration of thermal effects. Significant improvements in bearing performance were obtained with compliant bearings compared to white metal bearings. Furthermore, different polymer materials (PTFE, UHMWPE, pure PEEK and PEEK composite) were characterized using Frequency Response Function (FRF). It was shown that as the excitation frequency increased the equivalent stiffness was more or less constant while equivalent damping decreased exponentially. PTFE had similar equivalent stiffness compared to PEEK. As for equivalent damping, PTFE had slightly higher damping compared to PEEK or UHMWPE. Oil film thickness, oil film temperature and loads on tilting pad journal bearing were measured on 10 MW Kaplan hydroelectric power machine. Test results were compared to FEM model. It was shown that stiffness of the supporting structure may be more important to machine performance than the stiffness of the bearing alone.

  • 12.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Waukesha Bearings, United Kingdom .
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Ghent University, Belgium .
    Nonlinear dynamic behaviour of vertical and horizontal rotors in compliant liner tilting pad journal bearings: Some design considerations2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 82, 142-152 p.Article in journal (Refereed)
    Abstract [en]

    Dynamic behaviour of vertical and horizontal rotors in journal bearings with line pivot pads is investigated. Two bearing designs are compared: one with white metal pads and another with compliant liner pads. The influence of elasticity of the liner on the journal orbits is investigated. Some practical aspects of the compliant liner pad design are discussed. Compliant bearing design parameters such as preload factor, pivot offset, radial clearance, viscoelasticity, and pad inclination to control the size of the journal orbit are considered.

  • 13.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM).
    Novel materials in fluid film bearing design2015In: M2D2015: Proceedings of the 6th international conference on mechanics and materials in design, INEGI-FEUP , 2015, 2275-2276 p.Conference paper (Refereed)
    Abstract [en]

    This work shows how the use of novel materials, such as polymer composites and synthetic lubricants, in bearing design significantly improves bearing performance characteristics. Different bearing designs are considered. Improvements in main bearing performance characteristics, such as temperature, lubricant film thickness, load carrying capacity and power loss are presented. The effect of such design modifications on the bearing dynamic characteristics is considered. It is also shown that this approach allows a 50 % reduction in bearing power loss without sacrificing bearing safety.

  • 14. Filippov, Andrei
    et al.
    Azancheev, Nail
    Taher, Mamoun
    Shah, Faiz Ullah
    Rabet, Pauline
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM). Univ Ghent, Dept Mech Construct & Prod.
    Antzutkin, Oleg N.
    Self-diffusion and interactions in mixtures of imidazolium bis(mandelato)borate ionic liquids with polyethylene glycol: H-1 NMR study2015In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 53, no 7, 493-497 p.Article in journal (Refereed)
    Abstract [en]

    We used H-1 nuclear magnetic resonance pulsed-field gradient to study the self-diffusion of polyethylene glycol (PEG) and ions in a mixture of PEG and imidazolium bis(mandelato)borate ionic liquids (ILs) at IL concentrations from 0 to 10 wt% and temperatures from 295 to 370 K. PEG behaves as a solvent for these ILs, allowing observation of separate lines in H-1 NMR spectra assigned to the cation and anion as well as to PEG. The diffusion coefficients of PEG, as well as the imidazolium cation and bis(mandelato) borate (BMB) anion, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state, while the lifetimes of the associated states of the ions and ions with PEG are less than similar to 30ms. Generally, increasing the concentration of the IL leads to a decrease in the diffusion coefficients of PEG and both ions. The diffusion coefficient of the anion is less than that of the cation; the molecular mass dependence of diffusion of ions can be described by the Stokes-Einstein model. NMR chemical shift alteration analysis showed that the presence of PEG changes mainly the chemical shifts of protons belonging to imidazole ring of the cation, while chemical shifts of protons of anions and PEG remain unchanged. This demonstrated that the imidazolium cation interacts mainly with PEG, which most probably occurs through the oxygen of PEG and the imidazole ring. The BMB anion does not strongly interact with PEG, but it may be indirectly affected by PEG through interaction with the cation, which directly interacts with PEG. Copyright (C) 2015 John Wiley & Sons, Ltd.

  • 15.
    Hjalmarsson, Nicklas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wallinder, Daniel
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Univ Ghent, Dept Mech Construct & Prod, B-9052 Zwijnaarde, Belgium.
    Atkin, Rob
    Aastrup, Teodor
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute Sweden, Stockholm, Sweden.
    Weighing the surface charge of an ionic liquid2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 38, 16039-16045 p.Article in journal (Refereed)
    Abstract [en]

    Electrochemical quartz crystal microbalance has been used to measure changes in the composition of the capacitive electrical double layer for 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate, an ionic liquid, in contact with a gold electrode surface as a function of potential. The mass difference between the cation and anion means that the technique can effectively "weigh" the surface charge accurately with high temporal resolution. This reveals quantitatively how changing the potential alters the ratio of cations and anions associated with the electrode surface, and thus the charge per unit area, as well as the kinetics associated with these interfacial processes. The measurements reveal that it is diffusion of co-ions into the interfacial region rather than expulsion of counterions that controls the relaxation. The measured potential dependent double layer capacitance experimentally validates recent theoretical predictions for counterion overscreening (low potentials) and crowding (high potentials) at electrode surfaces. This new capacity to quantitatively measure ion composition is critical for ionic liquid applications ranging from batteries, capacitors and electrodeposition through to boundary layer structure in tribology, and more broadly provides new insight into interfacial processes in concentrated electrolyte solutions.

  • 16. Wang, Yong-Lei
    et al.
    Shah, Faiz Ullah
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Ghent University, Belgium .
    Antzutkin, Oleg N.
    Laaksonen, Aatto
    Atomistic Insight into Orthoborate-Based Ionic Liquids: Force Field Development and Evaluation2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 29, 8711-8723 p.Article in journal (Refereed)
    Abstract [en]

    We have developed an all-atomistic force field for a new class of halogen-free chelated orthoborate-phosphonium ionic liquids. The force field is based on an AMBER framework with determination of force field parameters for phosphorus and boron atoms, as well as refinement of several available parameters. The bond and angle force constants were adjusted to fit vibration frequency data derived from both experimental measurements and ab initio calculations. The force field parameters for several dihedral angles were obtained by fitting torsion energy profiles deduced from ab initio calculations. To validate the proposed force field parameters, atomistic simulations were performed for 12 ionic liquids consisting of tetraalkylphosphonium cations and chelated orthoborate anions. The predicted densities for neat ionic liquids and the [P-6,P-6,P-6,P-14][BOB] sample, with a water content of approximately 2.3-2.5 wt %, are in excellent agreement with available experimental data. The potential energy components of 12 ionic liquids were discussed in detail. The radial distribution functions and spatial distribution functions were analyzed and visualized to probe the microscopic ionic structures of these ionic liquids. There are mainly four high-probability regions of chelated orthoborate anions distributed around tetraalkylphosphonium cations in the first solvation shell, and such probability distribution functions are strongly influenced by the size of anions.

  • 17. Simmons, Gregory F.
    et al.
    Varela, Alejandro Cerda
    Santos, Ilmar Ferreira
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Dynamic characteristics of polymer faced tilting pad journal bearings2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 74, 20-27 p.Article in journal (Refereed)
    Abstract [en]

    Dynamic characteristics of polymer faced tilting pad journal bearings are presented. Investigations are conducted using a single pad, load on pad configuration over a range of shaft speeds and loads. Two polyether ether ketone (PEEK) faced pads, one polytetrafluoroethylene (PTFE) faced pad and two entirely PEEK pads are investigated to determine the effect of varying mean bearing pressure and pivot characteristics as well as different material properties of the polymer layer. Experimental results indicate increased damping and decreased stiffness and slightly increased oil film temperature for entirely PEEK pads compared to pads with a PEEK lining and steel backing. Similar effects were observed by using a softer (PTFE) pad liner with a steel backing.

  • 18. Golchin, Arash
    et al.
    Nguyen, Tan Dat
    De Baets, Patrick
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Prakash, Braham
    Effect of shaft roughness and pressure on friction of polymer bearings in water2014In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 228, no 4, 371-381 p.Article in journal (Refereed)
    Abstract [en]

    In this study, the frictional behavior of selected commercially available unfilled polymers, namely, polyether ether ketone, polytetrafluoroethylene, polyethylene terephthalate, and ultra-high molecular weight polyethylene against an Inconel shaft was investigated using a journal bearing test configuration in water-lubricated sliding contact. Dynamic friction curves were obtained for various shaft roughness values and polymer combinations. The results showed a significant influence of shaft surface roughness on running-in and steady state friction in water-lubricated conditions. Contact angle measurements revealed a significant increase in wettability of Inconel counterfaces. The X-ray photoelectron spectroscopy (XPS) analysis of the surfaces suggests formation of a reaction layer on worn Inconel surfaces when sliding against the polymers. The influences of counter surface roughness and load on frictional response of polymers were studied through intermittent tests by obtaining dynamic and breakaway friction maps for different polymer materials, shaft roughness values, and pressure combinations. In general, a trend of decreasing friction was obtained with increasing contact pressure; however, the materials' frictional responses to variations in counter surface roughness were different. These results indicate that although a reduced counter surface roughness may be beneficial for dynamic friction of polymers in all lubrication regimes, it can adversely affect the materials' breakaway friction response.

  • 19. Simmons, Gregory F.
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Mueller, Michael
    Byheden, Åke
    Prakash, Braham
    Extending performance limits of turbine oils2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, 52-60 p.Article in journal (Refereed)
    Abstract [en]

    New turbine oils providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performance are investigated. Comparisons are made in both laboratory scale testing using typical journal bearing sliding surfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The results from these studies demonstrate the effectiveness of new, high VI, turbine oils for reducing friction at machine startup and improving performance during full film operation.

  • 20. Delgad, Y. P.
    et al.
    Staia, M.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Ghent University, Belgium.
    Bonny, K.
    Malek, O.
    Lauwers, B.
    Vleugels, J.
    De Baets, P.
    Friction and wear characteristics of advanced ceramic materials2014In: 5th World Tribology Congress, WTC 2013, 2014, 2171-2174 p.Conference paper (Refereed)
  • 21. Taher, Mamoun
    et al.
    Shah, Faiz Ullah
    Filippov, Andrei
    de Baets, Patrick
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Department of Mechanical Construction and Production, Ghent University, Belgium .
    Antzutkin, Oleg N.
    Halogen-free pyrrolidinium bis(mandelato) borate ionic liquids: some physicochemical properties and lubrication performance as additives to polyethylene glycol2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 58, 30617-30623 p.Article in journal (Refereed)
    Abstract [en]

    This work reports on the synthesis and physicochemical characterisation of novel halogen-free boron containing ionic liquids (hf-BILs) with dialkylpyrrolidinium cations [C(n)C(1)Pyrr](+), n = 4-14, and bis(mandelato) borate anion [BMB](-). All the synthesised compounds are liquids at room temperature. It was found that the thermal properties and density of these hf-BILs are affected by the length of the longest alkyl chain connected to the nitrogen atom in the pyrrolidinium cations. Differential scanning calorimetry measurements revealed that glass transition temperatures of these ionic liquids are in the temperature range from 218 to 241 K. Interestingly, the glass transition temperatures follow the "odd-even" effect related to the number of carbons (n) in one of the alkyl chains of [CnC1Pyrr]+. It was also found that hf-BILs' density decreases with an increase in the alkyl chain length of [CnC1Pyrr]+. It is suggested that the "odd-even" effect is associated with the difference in packing and specific interactions of cations and anions of this class of hf-BILs. Their lubricating properties, as 3 wt% additives in polyethylene glycol (PEG), were evaluated in steel-steel contacts. PEG with hf-BILs additive provided significantly lower wear and friction compared to the neat PEG and 5W40 engine oil. It was found that shortening the length of the longest alkyl chain in the cations of [C(n)C(1)Pyrr][BMB] significantly reduces frictional losses. Antiwear properties of [C(n)C(1)Pyrr][BMB] in PEG follow the same trend.

  • 22. Delgado, Y. P.
    et al.
    Staia, M.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Bonny, K.
    Malek, O.
    Lauwers, B.
    Vleugels, J.
    De Baets, P.
    High temperature friction response of PECS TiB2-B4C composite2014In: 5th World Tribology Congress, WTC 2013, 2014, 2189-2192 p.Conference paper (Refereed)
  • 23. Simmons, Gregory F.
    et al.
    Cha, Matthew
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Aidanpaa, Jan-Olov
    Cervantes, Michel J.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Department of Mechanical Construction and Production, Ghent University, Belgium.
    Steady state and dynamic characteristics for guide bearings of a hydro-electric unit2014In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 228, no 8, 836-848 p.Article in journal (Refereed)
    Abstract [en]

    Experiments are conducted using a 10-MW Kaplan hydropower machine which is outfitted with an extensive array of sensors to determine oil film thickness, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all journal bearings are compared to a commercial rotor dynamics model and results for the central journal bearing are compared to a multi-physics model to provide insight into the machine's steady state and dynamic characteristics and their variations during normal operation.

  • 24. Filippov, Andrei
    et al.
    Taher, Mamoun
    Shah, Faiz Ullah
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Ghent University, Belgium .
    Antzutkin, Oleg N.
    The effect of the cation alkyl chain length on density and diffusion in dialkylpyrrolidinium bis(mandelato)borate ionic liquids2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 48, 26798-26805 p.Article in journal (Refereed)
    Abstract [en]

    The physicochemical properties of ionic liquids are strongly affected by the selective combination of the cations and anions comprising the ionic liquid. In particular, the length of the alkyl chains of ions has a clear influence on the ionic liquid's performance. In this paper, we study the self-diffusion of ions in a series of halogen-free boron-based ionic liquids (hf-BILs) containing bis(mandelato)borate anions and dialkylpyrrolidinium cations with long alkyl chains CnH2n+1 with n from 4 to 14 within a temperature range of 293-373 K. It was found that the hf-BILs with n = 4-7 have very similar diffusion coefficients, while hf-BILs with n = 10-14 exhibit two liquid sub-phases in almost the entire temperature range studied (293-353 K). Both liquid sub-phases differ in their diffusion coefficients, while values of the slower diffusion coefficients are close to those of hf-BILs with shorter alkyl chains. To explain the particular dependence of diffusion on the alkyl chain length, we examined the densities of the hf-BILs studied here. It was shown that the dependence of the density on the number of CH2 groups in long alkyl chains of cations can be accurately described using a "mosaic type'' model, where regions of long alkyl chains of cations (named 'aliphatic' regions) and the residual chemical moieties in both cations and anions (named 'ionic' regions) give additive contributions. Changes in density due to an increase in temperature and the number of CH2 groups in the long alkyl chains of cations are determined predominantly by changes in the free volume of the 'ionic' regions, while 'aliphatic' regions are already highly compressed by van der Waals forces, which results in only infinitesimal changes in their free volumes with temperature.

  • 25. Cupillard, S.
    et al.
    Cervantes, M. J.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Thermohydrodynamic analysis of a journal bearing with a microgroove on the shaft2014In: Computational Thermal Sciences, ISSN 1940-2503, E-ISSN 1940-2554, Vol. 6, no 1, 47-57 p.Article in journal (Refereed)
    Abstract [en]

    In this study, thermohydrodynamic performance of a journal bearing with a microgroove created on the shaft is analyzed. A plain journal bearing is modeled using a computational fluid dynamics (CFD) software package. Navier-Stokes and energy equations are solved. The rotor-stator interaction is treated by using a computational grid deformation technique. The goal is to examine the pressure/temperature distribution in the bearing film. Results are presented in terms of typical bearing parameters as well as flow patterns. Results are also compared to the bearing with a smooth shaft. The effect induced by a microgroove on pressure distribution is explained for different bearing configurations, eccentricities, and microgroove depths. It is shown that the microgroove produces a local drop in pressure which, averaged over one revolution, decreases the load carrying capacity. The load carrying capacity is further decreased by using deeper microgrooves. With thermal effects considered, the microgroove carries more cold lubricant into the warmest regions of the bearing. This effect, more pronounced with deeper microgrooves, is due to a global flow recirculation inside the microgroove, which improves mixing.

  • 26.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kuznetsov, Evgeny
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    A comparative linear and nonlinear dynamic analysis of compliant cylindrical journal bearings2013In: Mechanism and machine theory, ISSN 0094-114X, E-ISSN 1873-3999, Vol. 64, 80-92 p.Article in journal (Refereed)
    Abstract [en]

    Dynamic behaviour of compliant cylindrical journal bearings is investigated using linear and nonlinear numerical approaches. Journal motion orbits based on linearized dynamic coefficients are compared to the journal trajectories obtained by the nonlinear transient analysis. Obtained results are presented in terms of orbit amplitude, shape and location. The influence of compliant liner thickness, viscoelastic properties and deformation model is also investigated. A linear model is found to deliver acceptable results at a relatively small shaft unbalance under low to average loads. However, with a journal amplitude motion greater than 37% of the bearing diametral clearance, the linear model should not be used to analyse journal transient motion. Plane strain hypothesis is found to be a proper substitute for a full deformation model when a compliant liner is thinner than 2 mm (for the bearing geometry used in this study). It was also shown that the liner viscoelasticity should be taken into account whenever a compliant liner is relatively thick (in our case, 2 mm). Viscoelasticity of the liner decreases journal amplitude compared to a pure elastic liner.

  • 27. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Antzutkin, Oleg N.
    Boron in Tribology: From Borates to Ionic Liquids2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 51, no 3, 281-301 p.Article, review/survey (Refereed)
    Abstract [en]

    Boron compounds are widely used in a range of tribological applications such as friction modifiers, antioxidants, antiwear additives, and in many cases as environmentally friendly lubricants. The chemical nature and structure of boron compounds provide multifunctionality. They are used as (1) solid lubricants such as boric acid and hexagonal boron nitride, (2) liquid lubricants such as ionic liquids, (3) lubricant additives such as borate derivatives of various organic and inorganic compounds, and (4) coatings such as cubic boron nitride and different metal borides. Boron is also one of the most favorable elements for coatings and thin films in biotribological and biomedical applications. This review outlines the growing role of boron in lubrication over the past several decades, summarizes the main findings, and identifies future challenges related to boron chemistry.

  • 28. Golchin, A.
    et al.
    Nguyen, T. D.
    De Baets, P.
    Prakash, B.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Effect of shaft roughness and pressure on friction of polymer bearings in water2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, 3153-3156 p.Conference paper (Refereed)
  • 29.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Isaksson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, 46-53 p.Article in journal (Refereed)
    Abstract [en]

    The effect of pad compliance on the dynamic response of tilting pad journal bearings is investigated. Pad compliance is varied by changing pivot geometry and Young's modulus of pad backing and pad liner. Two pad support configurations are considered: one that allows only circumferential tilt and another one that allows both circumferential and axial tilts. Journal orbits, oil film pressure and oil film thickness are compared and discussed. It is shown that higher pad backing compliance significantly increases the journal orbit size and results in an increase in oil film pressure while oil film thickness is decreased. With a compliant liner, oil film pressure is decreased while oil film thickness is increased. Tapers at the pad edges are essential to increase the global minimum oil film thickness in compliant liner bearings.

  • 30.
    Álvarez Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Cranston, Emily
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Niga, Petru
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Werzer, O.
    Sweeney, J.
    Hausen, F.
    Hayes, R.
    Webber, G. B.
    Endres, F.
    Bennewitz, R.
    Hjalmarsson, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Atkin, R.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Nanotribology: Tribotronics, ionic liquids and control of surface interactions2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, 3106-3108 p.Conference paper (Refereed)
    Abstract [en]

    The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.

  • 31. Filippov, A.
    et al.
    Shah, F. U.
    Taher, M.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Antzutkin, O. N.
    NMR self-diffusion study of a phosphonium bis(mandelato)borate ionic liquid2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 23, 9281-9287 p.Article in journal (Refereed)
    Abstract [en]

    Newly synthesised halogen-free boron based ionic liquids (hf-BILs) composed of chelated orthoborate anions and phosphonium cations have hydrolytic stability, low melting point and outstanding wear and friction reducing properties. We report here the peculiarities of self-diffusion in one representative from this class, trihexyltetradecylphosphonium bis(mandelato)borate, [P6,6,6,14][BMB], in the temperature range of its practical interest, 20-100 °C. NMR techniques demonstrated complicated diffusional behaviour-the ionic liquid can exist in one or two liquid "phases". In the low-temperature range (20-50 °C), two phases coexist where the cations, [P6,6,6,14], are contained mainly in the phase with slower diffusion coefficients while the anions, [BMB], are in the phase with faster diffusion coefficients. Cations have lower diffusion coefficients with a factor of 20 as compared with the anions, an effect which is caused by aggregation of cations into domains due to so-called "hydrophobic interaction" of their hydrocarbon chains. As the temperature rises above 60 °C, the two phases merge into one where both ions have equal diffusion coefficients. This is caused by thermal motion making the cation domains smaller in size and more easily interacting with anions. As a result, anions and cations diffuse in this high-temperature range as a pair.

  • 32. Simmons, G. F.
    et al.
    Aidanpää, J. -J
    Cervantes, M.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Operational transients in the guide bearings of a 10 MW Kaplan turbine2013In: International journal on hydropower and dams, ISSN 1352-2523, Vol. 20, no 5, 94-100 p.Article in journal (Refereed)
    Abstract [en]

    Experiments using a 10 MW Kaplan hydropower machine with a PowerFormerTM generator (the Porjus U9 research machine) are described. This machine has an extensive array of sensors to determine oil film thickness, pad tilting, pad load and oil temperature in all three guide bearings, as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all three guide bearings are examined during both steady-state and transient operation.

  • 33. Golchin, A.
    et al.
    Simmons, G. F.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Prakash, B.
    Tribological behaviour of polymeric materials in water-lubricated contacts2013In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 227, no 8, 811-825 p.Article in journal (Refereed)
    Abstract [en]

    This study aims at investigating the tribological behaviour of several unfilled polymer materials sliding against 316L stainless steel in distilled water. The tests were carried out in a unidirectional pin-on-disc configuration with an initial apparent contact pressure of 5MPa at room temperature. The worn surfaces were examined using scanning electron microscopy and energy dispersive spectroscopy techniques and the wear mechanisms were discussed. These studies indicate the occurrence of tribocorrosion of stainless steel during sliding against polypropylene. It is inferred that the frictional behaviour of the polymers is determined by both their wettability and solubility in water, where generally an increased hydrophobicity and relative energy difference with regard to water results in lower friction. The results from friction and wear tests show overall superior tribological performance of ultrahigh molecular weight polyethylene compared with the other polymeric materials in water.

  • 34. Sherrington, I.
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Tribotronics: The advent of a new paradigm for tribological systems?2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, 3200-3203 p.Conference paper (Refereed)
  • 35. Shah, F. U.
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Dean, P. M.
    MacFarlane, D. R.
    Forsyth, M
    Antzutkin, O. N.
    Halogen-free chelated orthoborate ionic liquids and organic ionic plastic crystals2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 14, 6928-6938 p.Article in journal (Refereed)
    Abstract [en]

    Five halogen-free orthoborate salts comprised of three different cations (cholinium, pyrrolidinium and imidazolium) and two orthoborate anions, bis(mandelato) borate and bis(salicylato) borate, were synthesised and characterised by DSC, X-ray diffraction and NMR. DSC measurements revealed that glass transition points of these orthoborate salts are in the temperature range from -18 to -2 degrees C. In addition, it was found that [EMPy][BScB] and [EMIm][BScB] salts have solid-solid phase transitions below their melting points, i.e. they exhibit typical features of plastic crystals. Salts of the bis(salicylato) borate anion [BScB](-) have higher melting points compared with corresponding salts of the bis(mandelato) borate anion [BMB](-). Single crystal X-ray diffraction crystallography (for [Chol][BScB] crystals) and solid-state multinuclear (C-13, B-11 and N-15) NMR spectroscopy were employed for the structural characterisation of [Chol][BScB], [EMPy][BScB] and [EMIm][BScB], which are solids at room temperature: a strong interaction between [BScB](-) anions and [Chol](+) cations was identified as (i) hydrogen bonding between OH of [Chol](+) and carbonyl groups of [BScB](-) and (ii) as the inductive C-H center dot center dot center dot pi interaction. In the other salt, [EMIm][BScB], anions exhibit pi center dot center dot center dot pi stacking in combination with C-H center dot center dot center dot pi interactions with [EMIm]+ cations. These interactions were not identified in [EMPy] [BScB] probably because of the lack of aromaticity in cations of the latter system. Our data on the formation of a lanthanum complex with bis(salicylato) borate in the liquid mixture of La3+(aq) with [Chol][BScB] suggest that this class of novel ILs can be potentially used in the extraction processes of metal ions of rare earth elements.

  • 36.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Journal vibration: Influence of compliant bearing design2012In: Proceedings Of The ASME 11th Biennial Conference On Engineering Systems Design And Analysis, Vol 4, 2012, 657-664 p.Conference paper (Refereed)
    Abstract [en]

    In this paper, the nonlinear dynamic behaviour of vertical and horizontal rotors in compliant tilting pad journal bearings has been investigated. White metal and compliant bearings with line pivot pads are compared. The dynamic response of four pad bearings with different preload factors is studied. The effect of viscoelasticity is also considered in comparison with purely elastic compliant and white metal liners. The influence of radial clearance and pad offset is analysed. It is shown how pad design parameters such as preload factor, pivot offset, viscoelasticity of the liner, and radial clearance can be selected to control the size of the journal orbit in compliant bearings.

  • 37.
    Cha, Matthew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Nonlinear Dynamic Response of Compliant Journal Bearings2012In: CSNDD 2012 – International Conference on Structural Nonlinear Dynamics and Diagnosis, EDP Sciences, 2012, 10005- p.Conference paper (Refereed)
    Abstract [en]

    This paper investigates the dynamic response of the compliant tilting pad journal bearings subjected to synchronous excitation. Bearing compliance is affected by the properties of pad liner and pad support geometry. Different unbalance eccentricities are considered. It is shown that bearing dynamic response is non-linear. Journal orbit complexity increases with pad compliance though the orbit amplitudes are marginally affected at low loads. At high loads, the journal is forced to operate outside the bearing clearance. The polymer liner reduces the maximum oil film pressure by a factor of 2 when compared to the white metal liner. The nonlinear dynamic response of compliant tilting pad journal bearings is thoroughly discussed.

  • 38. Shah, F. U.
    et al.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Antzutkin, O. N.
    Novel alkylborate-dithiocarbamate lubricant additives: Synthesis and tribophysical characterization2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 45, no 1, 67-78 p.Article in journal (Refereed)
    Abstract [en]

    Boron-based lubricant additives have recently received significant attention, because of their wear-reducing and frictional properties and low pollution. At the same time, dithiocarbamate complexes with different metals have a long history of being used as multifunctional additives to lubricants. In this study, novel, environmentally friendly additives containing alkylborate and dithiocarbamate groups with alkyl or methylbenzyl substitutes in one molecule were studied. Tribological tests were performed with the additives admixed in a mineral oil using steel-on-steel contacts in a four-ball tribometer. Borate derivatives of different dithiocarbamate ligands were synthesized by several step reactions to investigate tribochemical properties of boron, sulfur, and nitrogen combined in one selected compound. Viscous liquid products were characterized by multinuclear 1H, 13C, and 11B NMR spectroscopy. The surface morphology and the elemental composition of the tribofilms were investigated using an optical profiler and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). It was found that some of these novel compounds provide better antiwear performance and similar frictional properties compared with a commercially available ZnDTP package. Traces of sulfur in the tribofilms formed with both 0.2 and 1.0 wt% of alkylborate-dithiocarbamate compounds in a mineral oil were detected with EDS. 

  • 39.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Tribotronics: monitoring based active friction control2012In: Encyclopedia of Tribology, Springer-Verlag New York, 2012Chapter in book (Refereed)
  • 40. Golchin, Arash
    et al.
    Simmons, Gregory F.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Break-away friction of PTFE materials in lubricated conditions2011In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 48, 54-62 p.Article in journal (Refereed)
    Abstract [en]

    This study investigates the tribological characteristics at initiation of sliding (break-away friction) of several polytetrafluoroethylene based materials. Four PTFE composites, pure PTFE, and white metal were tested in a reciprocating tribo-meter with the block on plate configuration against a steel counter-surface. Apparent contact pressure and oil temperature were varied from 1 to 8&#xa0;MPa and 25 to 85&#xa0;°C respectively. SEM investigations revealed wear patterns of the PTFE materials and the abrasive nature of hard fillers. Bronze filled, carbon filled, and pure PTFE were found to provide lower break-away friction and less variation over the course of testing and generally superior properties.

  • 41. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Höglund, Erik
    Lindberg, Mats
    Antzutkin, Oleg N.
    Interfacial Antiwear and Physicochemical Properties of Alkylborate-dithiophosphates2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 4, 956-968 p.Article in journal (Refereed)
    Abstract [en]

    Boron compounds have become of interest in tribology because of their unique tribochemical and tribological properties. At the same time, dialkyldithiophosphates (DTPs) of transition metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Because of the environmental pollution and health hazards of these compounds, ashless compounds with reduced amounts of sulfur and phosphorus are desirable. This work reports on the synthesis, characterization, and tribological properties of a new class of compounds, alkylborate-dithiophosphates. This class combines two high-iron-affinity surface active groups, borate and dialkyldithiophosphate, into a single molecule. The final products, viscous liquids, were characterized by FT-IR, multinuclear 1H, 13C, 31P, and 11B NMR spectroscopy and thermal analyses. Residues of one representative compound from this class, DPB-EDTP, after thermal analyses were additionally characterized by multinuclear 13C, 31P and 11B MAS and 31P CP/MAS NMR spectroscopy. Solid-state NMR data suggest that a dominant part of the solid residue of DPB-EDTP consists of borophosphates. Antiwear and friction properties of a mineral oil with these novel additives were evaluated in a four-ball tribometer in comparison with O,O?-di-n-butyl-dithiophosphato-zinc(II), Zn-BuDTP, as a reference lubricant additive. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy-dispersive X-rays spectroscopy (SEM/EDS). The results show that alkylborate-dithiophosphates, with substantially reduced amounts of sulfur and phosphorus compared with Zn-BuDTP, have considerably better antiwear and friction performance.

  • 42. Antzutkin, O. N.
    et al.
    Shah, F. U.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Ionic-liquid-based lubricants and lubrication additives comprising ions2011Patent (Other (popular science, discussion, etc.))
  • 43. Shah, Faiz Ullah
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    MacFarlane, Douglas R.
    Somers, Anthony
    Forsyth, Maria
    Antzutkin, Oleg N.
    Novel halogen-free chelated orthoborate-phosphonium ionic liquids: synthesis and tribophysical properties2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 28, 12865-12873 p.Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis, characterisation, and physical and tribological properties of halogen-free ionic liquids based on various chelated orthoborate anions with different phosphonium cations, both without halogen atoms in their structure. Important physical properties of the ILs including glass transition temperatures, density, viscosity and ionic conductivity were measured and are reported here. All of these new halogen-free orthoborate ionic liquids (hf-BILs) are hydrophobic and hydrolytically stable liquids at room temperature. As lubricants, these hf-BILs exhibit considerably better antiwear and friction reducing properties under boundary lubrication conditions for steel-aluminium contacts as compared with fully formulated (15W-50 grade) engine oil. Being halogen free these hf-BILs offer a more environmentally benign alternative to ILs being currently developed for lubricant applications.

  • 44. Kusnetsov, E
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    On power loss reduction in journal bearings2011In: Condition Monitoring, Performance Improvement and Safe Operation of Bearings, 2011Conference paper (Refereed)
  • 45.
    Glavatskih, Sergei
    et al.
    Luleå University of Technology, Division of Machine Elements.
    Larsson, Roland
    SPECIAL ISSUE ON NORDTRIB: THE NORDIC SYMPOSIUM ON TRIBOLOGY 20102011In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 225, no J7, 563-564 p.Article in journal (Other academic)
  • 46. Simmons, Gregory
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Synthetic Lubricants in Hydrodynamic Journal Bearings: Experimental Results2011In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 42, no 1, 109-115 p.Article in journal (Refereed)
    Abstract [en]

    Synthetic lubricants and additives have seen many major improvements in recent years. However, very little is known about the performance peculiarities of these new lubricants in actual machines. To fill this gap, a new full-scale hydro-dynamic journal bearing test rig has been constructed to evaluate the behavior of conventional and new bearing designs, synthetic lubricants and variations in operating parameters. This test rig’s bearing has diameter 180 mm with measuring capabilities including continuous film thickness and film pressure as well as temperature. The new machine was used to compare a number of synthetic lubricants to mineral based lubricants, finding that performance of the synthetic lubricants was superior to their mineral based counterparts of much higher viscosity grade. These tests showed that high viscosity index (VI) synthetic lubricants had higher viscosity in the region of maximum pressure and lower viscosity elsewhere in the bearing than similar mineral based lubricants. This reduction in viscosity in low pressure zones was found to produce a measurable reduction in friction and power loss in the bearing system. This paper provides comparative performance results of several formulations of current and future turbine oils from measurements of losses, oil film thickness, and temperature under a range of operating parameters. Lubricants tested include ISO VG68 and VG32 mineral based turbine oils (VG68 and VG32), ISO VG32 synthetic ester based oil (SE32), two ISO VG22 synthetic ester based oils (SE22 and SV22), and ISO VG15 synthetic ester based oil (SE15). It was found that SE32 and VG68 provided similar performance at lower speeds while SV22 provided similar performance to VG68 at the highest speed. Likewise, SE22 and SV22 provided similar performance to VG32 at low speeds while SE15 provided similar performance to VG32 at medium to higher speeds. Generally, the results demonstrate the potential for replacing mineral based lubricants with high performance synthetic lubricants of significantly lower viscosity grade without sacrificing bearing safety.

  • 47. Kuznetsov, Evgeny
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Fillon, Michel
    THD analysis of compliant journal bearings considering liner deformation2011In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 44, no 12, 1629-1641 p.Article in journal (Refereed)
    Abstract [en]

    A numerical THD model is developed to investigate the effect of lining compliance on the bearing characteristics. The analysis shows increased load carrying capacity, significantly reduced peak pressures and thicker oil film in the loaded zone compared to a white metal bearing. Slightly thinner oil films are predicted at the bearing edges. Temperature and power loss are found to be similar for some load–speed combinations but higher for other operating conditions. It is also shown that load carrying capacity is more sensitive to thermal expansion while pressure and oil film thickness profiles are more sensitive to elastic deformation.

  • 48. Cupillard, Samuel
    et al.
    Cervantes, Michel
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Thermohydrodynamic analysis of a journal bearing with a microgroove on the shaft2011Conference paper (Refereed)
    Abstract [en]

    In this study, thermohydrodynamic performance of a journal bearing with a microgroove created on the shaft is analysed. A plain journal bearing is modelled using a computational fluid dynamics (CFD) software package. Navier-Stokes and energy equations are solved. The rotor-stator interaction is treated by using a computational grid deformation technique. Results are presented in terms of typical bearing parameters as well as flow patterns. Results are also compared to the bearing with a smooth shaft. The effect induced by a microgroove on pressure distribution is explained for different bearing configurations, eccentricities and microgroove depths. It is shown that the microgroove produces a local drop in pressure which, averaged over one revolution, decreases the load carrying capacity. The load carrying capacity is further decreased by using deeper microgrooves. With thermal effects considered, the microgroove carries more cold lubricant into the warmest regions of the bearing. This effect, more pronounced with deeper microgrooves, is due to a global flow recirculation inside the microgroove, which improve mixing.

  • 49.
    Glavatskih, Sergei
    et al.
    Luleå University of Technology, Division of Machine Elements.
    Kumar, Uday
    Tribotronics facilitates e-maintenance implementation2011In: Proceedings of the 24th International Congress on Condition Monitoring and Diagnosis Engineering Management: COMADEM 2011 / [ed] Maneesh Singh, Raj B.K.N. Rao, J.P. Liyanage, COMADEM International, 2011, 501-506 p.Conference paper (Refereed)
    Abstract [en]

    Our modern society depends to a great extent on the functionality and efficiency of all the mechanical machinery that we see around us and use every day. All these machines involve numerous tribological contacts. A contact between two surfaces that are in motion relative to each other will result in friction and wear.A constant trend towards more compact mechanical systems with higher power densities requires them to operate in increasingly severe conditions, which heavily influence tribological contacts. They, in turn, affect machine efficiency and impose a limit on machine reliability and service life. Present tribological systems are passive, i.e. their performance cannot be tuned on-line. The purpose of tribotronics is to control so-called loss outputs in a tribo-mechanical system: friction, wear, vibration, etc. Such a system includes sensors, a control unit and actuators. A tribotronic system is thus autonomous and self-adjusting. This allows for on-line tuning of the tribological components for the best performance. This paper illustrates how tribotronic systems can facilitate e-maintenance and thus provide foundation for the best maintenance decisions.

  • 50. Mill, O.
    et al.
    Dahlbäck, N.
    Worman, A.
    Knutsson, Sven
    Johansson, F.
    Andreasson, Patrik
    Yang, J.
    Lundin, U.
    Aidanpää, Jan-Olov
    Nilsson, H.
    Cervantes, Michel
    Glavatskih, Sergei
    Luleå University of Technology, Division of Machine Elements.
    Analysis and development of hydro power research synthesis within Swedish Hydro Power Centre2010Report (Other academic)
    Abstract [en]

    The market for hydropower re-investments in Sweden is approx 2.5 billion SEK/yr the coming decade. Large investments will also be carried out in Swedish tailing dams. This will result in challenging projects and need of experts. A crucial factor for a successful management of these challenges is the supply of engineers and researchers with hydro power and dam skills and knowledge. Swedish Hydro Power Centre (Svenskt vattenkraftcentrum, SVC) is a competence centre for university education and research environments within hydro power and mining dams. SVC comprises of two knowledge areas: Hydraulic Engineering and Hydro Turbines and Generators, respectively. SVC builds high-quality and long term sustainable knowledge at selected universities.

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