Ciliary propulsion of objects in tubes: wall drag on swimming Tetrahymena (Ciliata) in the presence of mucin and other long-chain polymers

The lubrication effect of three long-chain polymers - mucin, methylcellulose and Ficoll - on ciliary propulsion in tubes is measured by plotting the relative velocities of swimming cilitates as a function of the tube bore diameter. Mucin shows the most unequivocal lubrication, which is found at concentrations between 0% and 9.1% (w/v). This observation, coupled with viscometric measurements which show that ciliary tip shear rates are sufficient to solate mucin, serve as the groundwork for a model of mucin lubrication which explains the optimized lubrication behaviour of thixotropic gelating polymers as an expression of the response to shear by the various stages of polymer clustering during the gelatin process. In addition to the lubricative effect, another wall drag reduction effect by mucin was measured in the clearance region beyond the lubrication layer. This apparent viscosity reduction is optimized in the concentration range between 1.7% and 4.1% mucin and may also be explained in terms of the properties of gel clustering

Transient elastohydrodynamic lubrication analysis of a novel metal-on-metal hip prosthesis with a non-spherical femoral bearing surface

Effective lubrication performance of metal-on-metal hip implants only requires optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry

Journal bearing lubrication monitoring based on spectrum cluster analysis of vibration signals

Journal bearings are critical components for many important machines. Lubrication analysis techniques are often not timely and cost effective for monitoring journal bearings. This research investigates into vibration responses of such bearings using a clustering technique for identifying different lubrication regimes, and consequently for assessing bearing lubrication conditions. It firstly understands that the vibration sources are mainly due to the nonlinear effects including micro asperity collisions and fluid shearing interactions. These excitations together with complicated vibration paths are difficult to be characterized in a linear way for the purpose of condition monitoring. Therefore, a clustering analysis technique is adopted to classify the vibration spectrum in high frequency ranges around 10kHz into different representative responses that corresponds to different bearing modulus values and lubrication characteristics. In particular, the analysis allows sensitive signal components and sensor positions to be determined for monitoring the journal bearing effectively. Test results from self-aligning spherical journal bearings show that it allows different lubricant oils and different lubrication regimes to be identified appropriately, providing feasible ways to online monitoring bearing conditions

Identification of lubrication Regimes in Mechanical Seals using Acoustic Emission for Condition Monitoring

The quality of lubrication condition between seal faces directly affects the reliability, operating life and sealing performance of mechanical seals. Thus, the identification of lubrication regimes in face seals i.e. boundary lubrication (BL), mixed lubrication (ML) and hydrodynamic lubrication (HL) is of high importance for developing effective online condition monitoring approaches. This paper investigates the tribological behaviour and frictional characteristics of mechanical seals based on nonintrusive acoustic emission (AE) measurements. Mathematical models for AE generation mechanisms are derived based on the tribological behaviour and operating parameters of mechanical seals. They produce agreeable results with experimental data in explaining the types of AE signals observed in monitoring the face lubrication conditions. Frequency domain analysis of data shows that the viscous friction process generates more low frequency AE signals, whereas the asperity interactions show more high frequency AE. Moreover, the feasibility of using statistical parameters of the time domain data is shown to identify the lubrication regimes in face seals

Lubrication approximation for micro-particles moving along parallel walls

Lubrication expressions for the friction coefficients of a spherical particle moving in a fluid between and along two parallel solid walls are explicitly evaluated in the low-Reynolds-number regime. They are used to determine lubrication expression for the particle free motion under an ambient Poiseuille flow. The range of validity and the accuracy of the lubrication approximation is determined by comparing with the corresponding results of the accurate multipole procedure. The results are applicable for thin, wide and long microchannels, or quasi-two-dimensional systems.Comment: 4 pages, 5 figure

Lubrication in cold rolling: Elasto-plasto-hydrodynamic lubrication

A model has been developed with respect to hydrodynamic lubrication in cold rolling. The basic model describes the configuration of a rigid, perfectly plastic sheet rolled by a rigid work roll. The governing equations have been solved throughout the complete contact area, i.e. the inlet, the work zone and the outlet zone. Multi-level techniques have been applied to solve these equations together with boundary conditions, resulting in an algorithm solving the problem in O(n) operations. This means that the distribution of the pressure and the traction force in the lubricant film, and the shape of this film, as well as the plastic deformation of the sheet, can be accurately calculated for a large number of nodal points on a minicomputer. Subsequently elastic deformation, work hardening and dynamic behaviour of the flow stress have been incorporated in the model. It will be shown that the influence of these effects on the film thickness or the pressure distribution is considerable

Lubrication handbook

Information on lubricants from government reports, military specifications, qualified parts lists, and suppliers of commercial lubricants has been consolidated in one source. Handbook includes data on chemical and physical properties of solid, bonded solid, and liquid lubricants; dispersions and composites; and greases, oils, and hydraulic fluids