Proceedings of SerbiaTrib '13

Serbian TribologySocietySERBIATRIB ‘1313 th International Conference onTribologyKragujevac, Serbia, 15 – 17 May 2013Faculty of Engineeringin KragujevacEFFECT OF VISCOSITY ON ELASTOHYDRODYNAMICLUBRICATION BETWEEN PARALLEL SURFACES SUBJECTEDTO HIGH ACCELERATIONUsman Ali Zia 1 , Aamer A. Baqai 1 , Waseem Akram 11 National University of Science & Technology(NUST), Pakistanusman_ali442@hotmail.com, aamerbaqai1@gmail.com, wasim6@gmail.comAbstract:Material wear due to friction is one of the most commonly experienced causes of material failure inany mechanical industry. Various studies have been conducted and as a result of these studies variouslubrication solutions have been proposed. Present work is an attempt to propose an Elastohydrodynamiclubrication solutio20n for a frictional wear problem experienced in an industrial application involving thesliding contact between two parallel surfaces subjected to high acceleration. The “Numerical model formixed lubrication” developed by Dong Zhu in 1990s has been modified to accommodate the constraints ofproblem at hand. The solution proposed predict the lubricant film thickness that when maintained betweenthe contacting surfaces can avoid full metal contact, which in turn shall avoid the material wear. The presentresearch is an attempt to comprehend the effect of change of viscosity and change of clearance between thesurfaces on the value of film thickness. Different grades of nonflammable, anticorrosive Perfluoropolyetherbased grease (Krytox) are used. The results obtained are in the form of graphs which calculates the value offilm thickness for one complete slide of one surface over the other. The results obtained by the numericalmodel are compared and found well-in-accordance with the experimental data available and with theanalytical predictions made by scholars in the past.Keywords: Tribology, Friction, Elastohydrodynamic lubrication, Krytox, Shear stress factor, hydrodynamicpressure1. INTRODUCTIONWear is the major cause of material wastage andloss of mechanical performance and any reductionin wear can result in considerable savings. Frictionis a principal cause of wear and energy dissipation.Considerable savings can be made by improvedfriction control. It is estimated that one-third of theworld's energy resources in present use is needed toovercome friction in one form or another.Lubrication is an effective means of controllingwear and reducing friction. Principles studied underthe field of tribology helps to analysis suchproblems of frictional wear. Lubricationphenomenon is being used to avoid fricational wearsince the time of its discovery.For any tribological studies the lubricationregime in which that particular machine/application is working is very important as it steersthe later research in the field. The outcome of mostof these researches is a lubrication solution that ifmaintained between the contacting surfaces canavoid dry metal-metal contact and inturndiminishes the chances of any mechanical wear. Alubrication solution can be studied under two maintypes of regimes:Fluid Film Lubrication andBoundary Lubrication.Out of these regimes, the fluid film lubrication isconsidered in case the required factor of safety ishigh so it is desired that the two contacting surfaceshave minimum chances of coming in contact witheach other. This requires a thick lubrication layer(exceeding a thickness of more that 1um) [1]between the surfaces so that enough hydrodynamicpressure exists to keep the surfaces apart.13 th International Conference on Tribology – Serbiatrib’13 251