Mechanical Analysis of Lubrication and Lubricants
(2002) Abstract
 This thesis comprises three different topics within the field of tribology. First, design functions for analyses of slider bearings are developed. Second, a lubricant model applied to elastohydrodynamically lubricated (EHL) line contacts considering wallslip is presented. Finally, an experimental apparatus for investigations of lubricants at high pressures is presented.
The design of hydrodynamic bearings usually requires a total numerical analysis of the pressure distribution and the corresponding design quantities such as load capacity and power loss. The objective of this part of the thesis was to determine curvefitted functions describing each design quantity. Three different kinds of geometry were analysed;... (More)  This thesis comprises three different topics within the field of tribology. First, design functions for analyses of slider bearings are developed. Second, a lubricant model applied to elastohydrodynamically lubricated (EHL) line contacts considering wallslip is presented. Finally, an experimental apparatus for investigations of lubricants at high pressures is presented.
The design of hydrodynamic bearings usually requires a total numerical analysis of the pressure distribution and the corresponding design quantities such as load capacity and power loss. The objective of this part of the thesis was to determine curvefitted functions describing each design quantity. Three different kinds of geometry were analysed; rectangular tiltingpad thrust bearings, sectorshaped tiltingpad thrust bearings and journal bearings with two axial oil grooves. The approximate design functions obtained are shown to be in very good agreement with the numerically calculated results. The functions are intended to be implemented in short computer programs.
A wallslip model including limiting shear stress is presented. The lubricant model was applied to EHL line contacts using isothermal conditions. The main part of the model concerns the lubricant velocity at each surface that is decoupled from the corresponding surface velocity giving two new variables in the EHL equations. The lubricant velocity at the surface is related to the corresponding shear stress. As long as the value of the shear stress is below the limiting shear stress, the lubricant velocity is equal to the surface velocity. However, when the shear stress reaches the limiting shear stress, interfacial slip appears and the lubricant velocity differs from the surface velocity. Both smooth and wavy surfaces were used in the calculations and the influence of the wallslip model on the results compared to a Newtonian model was investigated.
Results from a high pressure chamber are presented. It is possible to use the apparatus for a number of different measurements. The compressibility variation with the pressure for five different lubricants was investigated for pressures up to 2.7 GPa. The density variation for each lubricant is presented as a curvefit. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/20678
 author
 Ståhl, Jonas ^{LU}
 supervisor
 opponent

 Dr Venner, Kees, Nederländerna
 organization
 publishing date
 2002
 type
 Thesis
 publication status
 published
 subject
 keywords
 vakuumteknik, vibrationer, Maskinteknik, hydraulik, akustik, Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering
 pages
 192 pages
 publisher
 Division of Machine Elements, Department of Mechanical Engineering, Lund Institute of Technology
 defense location
 Lund Institute of Technology, Mbuilding, Room M:B
 defense date
 20021129 09:15:00
 language
 English
 LU publication?
 yes
 id
 27438bfff31345c4a79f095f2882d2bd (old id 20678)
 date added to LUP
 20160404 09:59:29
 date last changed
 20181121 20:56:05
@phdthesis{27438bfff31345c4a79f095f2882d2bd, abstract = {This thesis comprises three different topics within the field of tribology. First, design functions for analyses of slider bearings are developed. Second, a lubricant model applied to elastohydrodynamically lubricated (EHL) line contacts considering wallslip is presented. Finally, an experimental apparatus for investigations of lubricants at high pressures is presented.<br/><br> <br/><br> The design of hydrodynamic bearings usually requires a total numerical analysis of the pressure distribution and the corresponding design quantities such as load capacity and power loss. The objective of this part of the thesis was to determine curvefitted functions describing each design quantity. Three different kinds of geometry were analysed; rectangular tiltingpad thrust bearings, sectorshaped tiltingpad thrust bearings and journal bearings with two axial oil grooves. The approximate design functions obtained are shown to be in very good agreement with the numerically calculated results. The functions are intended to be implemented in short computer programs.<br/><br> <br/><br> A wallslip model including limiting shear stress is presented. The lubricant model was applied to EHL line contacts using isothermal conditions. The main part of the model concerns the lubricant velocity at each surface that is decoupled from the corresponding surface velocity giving two new variables in the EHL equations. The lubricant velocity at the surface is related to the corresponding shear stress. As long as the value of the shear stress is below the limiting shear stress, the lubricant velocity is equal to the surface velocity. However, when the shear stress reaches the limiting shear stress, interfacial slip appears and the lubricant velocity differs from the surface velocity. Both smooth and wavy surfaces were used in the calculations and the influence of the wallslip model on the results compared to a Newtonian model was investigated.<br/><br> <br/><br> Results from a high pressure chamber are presented. It is possible to use the apparatus for a number of different measurements. The compressibility variation with the pressure for five different lubricants was investigated for pressures up to 2.7 GPa. The density variation for each lubricant is presented as a curvefit.}, author = {Ståhl, Jonas}, language = {eng}, publisher = {Division of Machine Elements, Department of Mechanical Engineering, Lund Institute of Technology}, school = {Lund University}, title = {Mechanical Analysis of Lubrication and Lubricants}, year = {2002}, }