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Digitized by Kansas Correctional Industries

In this study, a model has been developed for the elastohydrodynamic lubrication with binary mixtures of compressible fluids, which can be used to represent emulsions with suspended deformable particles. The coupled modified Reynolds, elasticity, and rheology equations are solved simultaneously by combining the advanced multilevel method and the Newton-Raphson method. The effects of speed, load, dimensionlesss materials parameter, inlet oil volume fraction, droplet radius, surface tension group, elasticity of mixture, and equivalent viscosity models of emulsions on the lubrication characteristics of the emulsions are investigated. The speed, load, and oil volume fraction combinations studied in this study represent a broad range of operating conditions previously not investigated. The results of this study are in good agreement with the tests conducted by Kimura et al. and Zhu et al. indicating the effects of droplet radius of oil phase and the speed on the film thickness. The film thickness increases with increasing droplet size for the droplet size smaller than the film thickness. At the low oil volume fraction and low speed, the oil volume fraction increases rapidly with coordinate x to form the oil pool in the region close to the Hertzian contact area. With the increase of speed, the extent of the oil pool decreases significantly so that the oil volume fraction at the contact area decreases rapidly. Consequently, the film thickness also decreases due to the decrease in the effective viscosity of the mixture. When the speed is getting higher, the oil and water phases enter the contact conjunction so that the oil volume fraction is closer to the inlet one.

Inaug.-diss.--Eidgenössische technische hochschule, Zürich. / Lebenslauf.

An extensive literature survey of the subject of gear dynamics is undertaken and the increasing recognition of the role of the lubricating oil film in this field, especially as a damping source, is highlighted. The oil film separating the mating surfaces of involute spur gears is analysed assuming hydrodynamic conditions, rigid teeth (as far as the film shape is concerned) and pressure dependent viscosity. Gear tooth mesh stiffness is expressed as a function of the dynamic load and the position of contact. simple model of a pair of spur gears is subjected to a transient response analysis and the behaviour of the lubricating oil film observed. According to the motions of equivalent masses of the apars under these transient conditions damping due to the oil film is determined. The numerical solutions obtained at various operating conditions are combined to form an approximate formula to predict the damping ratio in terms of the dynamic tooth load, rolling speed of the tooth surfaces and the viscosity of the lubricating oil. A digital computer simulation of the dynamic motion of the pair of gears is carried out incorporating the above damping ratio formula. The actual load sharing between the pairs of teeth (when more than one pair of teeth are in mesh), considering the tooth deflections, pitch errors, oil film thicknesses and the differences in mesh stiffnesses, is taken into account. The variations of the total maximum dynamic load and the maximum tooth load are studied under different nominal loads, contact ratios, oil viscosities and pitch errors over a wide range of speeds covering the resonance area. The variations of the dynamic load, individual tooth load, mesh stiffness and the oil film thickness during complete mesh cycles are also analysed under different operating conditions to identify particular areas where high loads and minimum film thicknesses occur. Theoretical results are compared with the experimental results obtained on a back-to-back gear test rig.

An efficient and robust predictive technique has been developed for the analysis of dynamically loaded, flexible journal bearings using the finite element method. The work is in two parts. In the first part a fast predictive technique is developed for the analysis of dynamically loaded, rigid journal bearings. The finite element formulation of Reynolds equation is presented using both 3-node triangular and 8-node isoparamteric elements to model the lubricant film. The latter are shown to approximate the problem more closely using fewer nodal points and hence requiring fewer equations. The Gauss-Seidel over-relaxation method is used to solve the resulting system equations and the sparseness of these equations is exploited. Comprehensive results are presented for the Ruston and Hornsby 6VEB Mk ifi marine diesel engine connecting rod bearing. Two different time stepping methods are considered and the effects of incorporating various oil feed features in the analysis are also presented. The second part of the work deals with the flexible bearing problem. The method of carrying out the structural modelling and the way in which the structural compliance relationships are obtained is described. A fast matrix inversion technique used to obtain these relationships is also described. Based on the rigid bearing work 8-node isoparametric elements are used to model the lubricant film. Two methods are presented for coupling the structural and lubrication analysis. The first method, the under-relaxation method, although proving straightforward to implement is shown to be unsatisfactory for this particular problem due to to convegnence problems. The second method is the Newton-Raphson method which is shown to be highly convergent. The Newton-Raphson method is subsequently highly modified to produce a fast solution method. This is shown to be several orders of magnitude faster than any previously developed method making this technique viable as a general design tool rather than just providing benchmarks against which to compare simpler analysis techniques. Again results are presented for the Ruston bearing showing the effect upon the predicted performance of incorporating elasticity into the analysis.

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