On the pressure projection in elasto-hydrostatic lubrication problems—Part 2: FE approximation to observe the pressure projection

We have argued in Part 1 that the conventional Reynolds equation including the deformation of elastic disc does not obtain the pressure spike. However, as the experimental results in some papers have found the pressure projection, it can be intuitively explained as being caused by something hard in the oil film; by the pressure sensor, namely, manganin; or by the solidified lubricant. In this paper, the first of these possible causes is analyzed, for the first time, by introducing the fluid velocity variable in the direction of the oil film thickness and using the solid–fluid coupled finite-element (FE) method. It is shown by the numerical results based on Hamilton's experimental data that the pressure projection can be obtained by introducing the thickness of the pressure sensor, and that the projection profile varies with the sensor location on the disc. However, to solve the non-linearity of lubricant viscosity accurately is left for future research because the above FE analysis does not converge with the experimental data.     

The finite volume solution of the Reynolds equation of lubrication with film discontinuities

The present work deals with the numerical solution of the Reynolds equation of lubrication in the specific case where the film thickness is discontinuous. The present approach is obtained within the framework of a finite volume discretization and enables concentrated inertia effects to be taken into account, as described by a generalized Bernoulli equation. The classic finite volume formulation is included as a special case when discontinuities are absent. Some numerical examples show that the conservative properties of the finite volume discretization are maintained even when the pressure field is discontinuous. A typical application shows that the film discontinuities should always be taken into account in a consistent physical manner in order to eliminate the awkward question of their impact on global results of technological interest.     

Analyses of thermal hydrodynamic lubrication in high-speed rolling. Part I: the effect of the roller's elastic deformation

A study of thermal hydrodynamic lubrication for high-speed strip rolling, which includes the roller's elastic deformation, was developed for a lubricant whose rheological behaviour satisfies the Barus' model. The difference in lubricating performances between an elastic roller and a rigid roller was assessed using parameters such as film thickness and pressure; temperature distributions in the fluid film, roller, and workpiece; separating force and shear torque. The elastic roller was made either of a unique material or its substrate was coated with one layer of a harder material to improve the wear resistance. The elastic deformation of the roller was obtained with the aid of Hitchcock's elastic-deformation theory and the biharmonic equation of Airy's stress function. It was found that the elastic deformation produces a substantial effect on some rolling characteristics.     

Analysis of pressure distribution for the various gas flow vacuum system in the range from 1 Pa to 133 Pa

The measurement and control of gas flow are critical in many manufacturing processes. Semiconductor manufacturers, in particular, require a number of different process gases for etching, deposition, oxidation, doping and inerting applications. In many of these, as well as other industrial and research processes including measurement of partial pressures with residual gas analyzers (RGAs), calibration of vacuum gauges, and conductance of a conductance-reducer , accurate measurement and stability of the gas pressure within the reaction vacuum chamber is essential. In the present work, pressure distribution in the chamber of a newly developed flow control system was investigated for three gases (Ar, N₂, and He) range from 1 Pa to 133 Pa. For all the gases, the relative deviations in pressure distribution near the gas inlet and outlet were in the range of −1.3% and 1.2% respectively.     

On the compressive behaviour of sintered porous coppers with low to medium porosities—Part I: Experimental study

A space holder method in power metallurgy has been used to prepare porous coppers of low to medium porosities with good control of pore size, shape as well as distribution. The compressive properties of the porous coppers have been investigated. While the modulus is found to decrease in terms of porosity, it appears to be insensitive to powder size. The yield strength shows a linear relationship with porosity, and is found to follow a Hall–Petch relationship with powder size. The deformation mechanism of the porous metals has been studied by a displacement controlled uniaxial compression. Results show that under a quasi-static condition, porous coppers with low to medium porosities deform homogeneously throughout the material, behaving more like a solid metal rather than a foam material. This paper focuses on the experimental study of the compressive strength of the porous coppers. Details of the preparation of sample materials and the microstructure study, as well as constitutive modelling are to be presented elsewhere.     

Performance of synthetic oils in the hydrodynamic regime — 1. experimental

An investigation of the performance of environmentally adapted synthetic oils in the hydrodynamic lubrication regime has been carried out. Four oils have been tested: polyalphaolefin and ester based ISO VG46 oils as well as mineral ISO VG68 and VG46 oils. Tests were conducted in a facility containing two identical tilting‐pad thrust bearings typical of the design in general use. The differences between the mineral and synthetic oils in terms of maximum operating temperature, minimum oil film thickness, and bearing power loss have been examined. Substitution of the mineral ISO VG68 oil with an ISO VG46 oil slightly reduces the bearing operating temperature. This is due to a decrease in the basic viscosity. It is concluded that the ester base ISO VG46 oil can be used as an environmentally adapted replacement for the mineral ISO VG68 oil without sacrificing bearing safety. Such a change also offers noticeable energy savings. If the ester based oil is used instead of a mineral oil of the same viscosity grade, bearing reliability is improved by the increased oil film thickness.     

Analysis of thick-walled cylindrical pressure vessels under the effect of cyclic internal pressure and cyclic temperature

A problem common to the pressure vessels' designer is the evaluation of stresses due to the effect of both cyclic temperature and pressure. This paper presents a complete analysis of stresses within the wall of a cylindrical pressure vessel subjected to cyclic internal pressure and temperature. The time-dependent stress distribution is obtained using a numerical model on the basis of the forward finite difference technique. The influence of the working parameters, such as mean pressure and mean temperature, pressure and temperature amplitudes, diameter ratio, etc. on the effective stress is studied. The relation between the mean stress and stress amplitude is obtained for different working conditions. The relation between the working parameters according to Soderberg criteria is presented. An approximate expression for the relation between the working parameters is introduced in a simple and direct form. The results of the approximate solution are found to fit well with the numerical findings.