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The tribological study of Bonded Solid Lubricants, BSLs is reviewed, this includes a review of the constituent components of a BSL including a table of publications which presents a list of papers containing detailed data about the friction and wear of BSL coatings. The general theories of friction for metals in sliding contact and the friction theory applied to solid film lubrication are reviewed. A section is also included on Herzian contact theory and its application to solid films. A screening test is described for 12 BSLs applied to commercial components. This programme provided information on the friction coefficient and allowed the selection of one of these finishes for a further more in depth study. In general the friction coefficients obtained were higher than those quoted by the material manufacturers, it was presumed that this was due as the consequence of differences in test methods. Three test programmes are described that were conducted on a new pin on disc facility, a major programme to study the performance under various conditions at pressures above the yield pressure of the film. The information was used in the formulation of an empirical equation that can be used to predict the friction coefficient. This programme also demonstrated: that there were three distinct phases of performance, contact life increased with high loads and increased velocity, the friction coefficient in the steady state phase was between 0.18 and 0.22. The second programme examined the evolution of the wear scar on the ball and wear track on the disc. The programme illustrated the development of a transfer film on the ball and the steady increase in friction coefficient to a point where it became stable and the wear scar on the ball changed to a circular flat. The third programme investigated the friction coefficient at very low loads that produced pressures below or close to the yield pressure of the film. The results from this programme demonstrate that as the load increases, the friction coefficient decreases, this can be attributed to the Hertzian contact area being proportional to the load 213 and the friction force is proportional to the area, then the friction coefficient F/W is proportional to the load W-1/3. In the penultimate chapter theoretical predictions for the friction coefficient under various contact conditions are compared with the experimental results obtained, in general the calculated results are higher and some possible causes are given for the discrepancies.

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Different aspects of Elastohydrodynamic Lubrication (EHL) are studied. For smooth surfaces, a novel approach which solves separately the inlet and outlet regions by using the fracture mechanics equations, is proposed to solve EHL line contacts for shape and pressure. For rough surfaces, the full EHL geometry is reduced to an infinitely long contact with known mean film thickness and pressure; so real-roughness steady state analyses are carried out by considering the separate Fourier components of roughness and pressures, transient analysis by applying general finite difference methods. The subsurface stresses under micro-EHL are also calculated and given in form of a probability rather than a specific value and location. Initially, full-geometry EHL line contacts of smooth surfaces are studied. The spike of pressures is assumed to be singular and the idea is to start with an original Hertzian pressure distribution, then the edges of this pressure are truncated and the effects calculated via linear fracture mechanics; after this, the removed pressures are replaced by the converged inlet and outlet pressures, previously obtained by iterating the Reynolds and fracture mechanics equations. It is found that the outlet pressures follow a modified logarithmic function and therefore the exit bump in the shape joins the parallel film zone with a finite value of slope, unlike the Greenwood extension of Grubin's theory. From a set of solutions, the behaviour of the pressure spike as a function of two dimensionless numbers is followed. Comparisons with results from full numerical solutions are shown, giving good agreement. The scheme is later extended to consider compressibility and the Roelands viscosity law. After reducing full EHL geometry, the effects of real and wavy roughness in microEHL of Newtonian and Eyring fluids with or without compressibility are studied. Steady state analyses of real roughness show that only the high frequency components remain after deformation. By linearizing the Reynolds- Eyring equation an analytical solution is obtained and a criterion for the deformation of the roughness in EHL is given; from this, it is shown that the deformation is very much dependent on the ratio λ/ħ, obtaining little deformation for low values of it. Transient analyses of roughness in lubrication are also carried out considering the infinitely long contact. It is found that the transient pressure and film distributions are made of two parts: a) the well known steady state solution, plus b) a complementary function depending only on the modulation of film and pressures from the inlet. It is shown that the conclusions outlined for some authors (e.g. Venner and Lubrecht) about pressures travelling with the velocity of the roughness but shape with the average velocity of the lubricant, are only a particular case of a more general understanding. It is now believed that there is no a real physical damping in the transient shape.

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This thesis presents friction and wear rate measurements of the copper based bearing materials used in thrust bearing of aircraft fuel pumps. Highly detailed friction and wear data was collected from 20% and 30% lead in bronze (leaded bronze) substrates and 10% indium in lead (lead/indium) coated leaded bronze substrates in unlubricated and marginally lubricated conditions. Measurements were made under a wide range of load and speed using a thrust washer test apparatus and pin on disc test equipment.