| 1. |
- Almqvist, Andreas, et al.
(författare)
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On the dry elasto-plastic contact of nominally flat surfaces
- 2007
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 40:4, s. 574-579
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Tidskriftsartikel (refereegranskat)abstract
- A model to be used for numerical simulation of the contact of linear elastic perfectly plastic rough surfaces was developed. Energy dissipation due to plastic deformation is taken into account. Spectral theory and an FFT-techique are used to facilitate the numerical solution process. Results of simulations using four two-dimensional profiles with different topographies in contact with a rigid plane for a number loads are reported. From the results it is clear that the real area of contact (Ar) changes almost linearly with load and is only slightly affected by the difference in topography. A plasticity index is defined as the ratio of plastically deformed area (Ap) and Ar. Plastic deformation occurs even at low loads and there is a significant difference in plasticity index between the surface profiles considered. An investigation on how the spectral content of the surface profile influences the results presented is also performed. This is to ensure that the metrological limitations of the optical profilerused to measure the surfaces do not have a significant influence. It is concluded that the highest frequencies of the measured profile have a negligible influence on the real area of contact.
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| 2. |
- Almqvist, Torbjörn, et al.
(författare)
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THD analysis of tilting pad thrust bearings : comparison between theory and experiments
- 2000
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Ingår i: Journal of tribology. - : ASME International. - 0742-4787 .- 1528-8897. ; 122:2, s. 412-417
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present research is to verify a THD model of hydrodynamic thrust bearings. The developed model of a pivoted pad bearing, which can tilt both radially and circumferentially, allows for three-dimensional temperature distribution in the oil film and in the pad, as well as two-dimensional temperature variation in the runner. Viscosity and density are treated as functions of both temperature and pressure. Experiments have been performed on a test rig, containing two identical equalizing pivoted pad thrust bearings. Power loss, runner temperature, and pressure profiles as a function of load and rotational speed are compared for both theoretical and experimental investigations. Fairly good agreement has been found when the oil inlet temperature and heat transfer coefficients have been estimated in order to get the same runner temperature in both theory and experiment.
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| 3. |
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| 4. |
- Antzutkin, Oleg, et al.
(författare)
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Ionic-liquid-based lubricants and lubrication additives comprising ions
- 2012
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Patent (populärvet., debatt m.m.)abstract
- Anti-wear and friction-reducing lubricants and additives to lubricants for both ferrous and non-ferrous materials with/without DLC (diamiond-like-coatings) or graphene-based coatings, which are halogen free boron based ionic liqs. comprising a combination of an anion chosen from a mandelato borate anion, a salicylato borate anion, an oxalato borate anion, a malonato borate anion, a succinato borate anion, a glutarato borate anion and an adipato borate anion, with at least one cation selected from a tetraalkylphosphonium cation, a choline cation, an imidazolium cation and a pyrrolidinium cation, wherein said at least one cation has at least one alkyl group substituent with the general formula CnH2n+1 , wherein 1≤n≤80. Advantages of the invention include that it provides halogen free ionic liqs. for lubrication and that sensitivity for hydrolysis is reduced.
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| 5. |
- Cervantes, Michel, et al.
(författare)
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Group dynamics [hydro power equipment]
- 2005
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Ingår i: International Water Power and Dam Construction. - 0306-400X. ; 57:12, s. 40-45
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An interdisciplinary research group was created at the Lulea University of Technology in Sweden to help develop world leading competencies and knowledge for cutting-edge technologies in hydro power generation. Based on the studies of this Swedish research group, this paper provides a description of the power system from a dynamic point of view to obtain an overall picture, and is completed with a detailed description of the bearings and turbines. The state-of-the-art in each field is presented, together with suggestions for further development.
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| 6. |
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| 7. |
- Glavatskikh, Sergei B., et al.
(författare)
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Oil film thickness measurement by means of an optic lever technique
- 2000
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 13:1, s. 23-35
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Tidskriftsartikel (refereegranskat)abstract
- Oil film thickness in hydrodynamic bearings is a fundamental parameter influencing overall hydrodynamic bearing performance. Knowledge of this thickness allows bearing performance to be optimized. For the small hydrodynamic bearings that are usually used in laboratory test facilities, a very small sensor (e.g., <2 mm) is required because of space limitations. Commercially available eddy-current and capacitance sensors are too large to be mounted in the pad of such a bearing. An alternative approach is to use sensors based on optical methods, such as the optic lever technique. The main idea in this technique is to detect the intensity of a light beam reflected from a target surface. This intensity is a function of the distance between the sensor and the target. This paper reports the specific features of the optic lever technique as used for measurements of oil film thickness. The design, calibration procedure, and main characteristics of an optical sensor are discussed. A test rig for the calibration of oil film thickness sensors is also presented. The sensor response curve has two parts, linear and non-linear; using the linear part results in high sensitivity in the micrometre range. The influence of different types of oil on the output signal of the sensor has also been investigated. Experiments with different target velocities have shown that this sensor can be used for accurate and reliable measurement of oil film thickness in hydrodynamic bearings
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| 8. |
- Glavatskikh, Sergei B.
(författare)
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On the hydrodynamic lubrication in tilting pad thrust bearings
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The primarily objective of this work was to investigate the performance of environmentally adapted synthetic oils in the hydrodynamic lubrication regime. A special test facility has been designed and manufactured for this purpose. The facility contains two equalising tilting pad thrust bearings typical of design in general use. One of the bearings is instrumented with thermocouples, pressure and oil film thickness sensors. Three thermistors and two pressure sensors are installed in one of the shaft collars. Power losses are measured by monitoring bearing friction torque and by the calorimetric technique. All sensors are connected to a PC based high-speed data acquisition system. The facility allows a complete set of bearing operating parameters to be obtained. Bearing characteristics in steady state and transient operating conditions were investigated at different load-speed combinations as well as at various supplied oil temperatures and flow rates. Steady state results were compared with the outputs of THD and TEHD theoretical models. The agreement was found to be good. Tests were run to find a possible replacement of ISO VG68 mineral oil currently used in thrust bearing units of hydroelectric power stations. Oils tested included mineral base ISO VG68 and ISO VG46 oils, PAO and ester base ISO VG46 oils. Tests showed that a change from VG68 oil to the lower viscosity grade oil reduces bearing peak temperatures. It is also shown that the energy savings associated with the use of VG46 oil in place of VG68 are significant. However, such a change may only be justified for the ester base oil since it gives as thick oil films as mineral oil ISO VG68 does. Alternatively, if the ester base oil is used instead of a mineral oil of the same viscosity grade bearing reliability is increased due to the increased oil film.
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| 9. |
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| 10. |
- Shah, Faiz Ullah, et al.
(författare)
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Antiwear additives for lubricants
- 2011
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Patent (populärvet., debatt m.m.)abstract
- The additives are described by the general formula (I) with 2≤k≤20, 1≤n≤20, R1 = CmH2m+1; 1≤m≤80, and R2 = CpH2p+1; 1≤p≤80.
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