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This thesis describes the results of a combined theoretical and experimental investigation into the thermohydrodynamic behaviour of a twin axial groove cylindrical bore journal bearing. The theoretical work involved the solution or Reynolds equation and energy equation where appropriate in two dimensions using the finite element method. Several numerical studies for isothermal conditions were then carried out to examine the film incompleteness effects on the bearing global behaviour and which demonstrated the considerable sensitivity with respect to loading vector. Concurrently, an experimental journal bearing test rig was developed for the required experiments. It has a bush diameter of 75.3mm and uses two shafts to give nominal clearance ratios of 0.002 and 0.004. The bush was comprehensively instrumented with thermocouples to give detailed information of bearing and white metal temperatures. Experiments were conducted successfully to obtain lubricant flow rate, bush torque reaction, journal load capacity and journal position for varying shaft speed and loading direction, and this demonstrated experimentally the sensitivity with respect to load vector and provided boundary conditions for thermal models. Two thermal models were developed and these suggested that, at a prescribed eccentricity ratio, a very significant load increase can occur (threefold) for a small change in loading direction. Additionally, predicted side flow is very load direction dependent while bush torque reaction is not. These predicted trends are confirmed by experimental observation and it was found that a rigorous thermohydrodynamic model gave the most close agreement between absolute measured and predicted bearing performance.

The current study represents a full investigation into the behaviour of a fluid film squeezed between two circular parallel plates by normal velocity which is produced by three types of loading condition: steadily-applied, impact-loaded, or oscillatory motion, in which the fluid in between the two plates is considered to be Newtonian or non-Newtonian and the solid boundary materials used are either both rigid or one of them is flexible. A mathematical model has been developed to include the effect of the fluid inertia, non-Newtonian fluid film, and flexibility of the solid material in determining the behaviour of a squeeze film bearing. The non-Newtonian power law model has been adopted in the current theoretical analysis, and the compliant surface bearing has been simulated in terms of the deflection of a mild steel diaphragm. The theoretical analysis was also developed to demonstrate the generation of the steady-state force generated in the oil film when it was subjected to an oscillatory squeeze motion and to show the distinction between a fixed and a free bearing system. The theoretical results are presented in graphical form to demonstrate the behaviour of the squeeze film bearing for different lubrication properties and solid material condition in which a comparison of conventional bearing behaviour with compliant surface, non-Newtonian fluid behaviour has been carried out. An experimental test rig was modified to permit a wide range of experiments to be performed utilising up-to-date, computerised data collection and manipulation procedures. A series of tests were carried out and a comparison of the results was made with predicted theoretical solutions and published work. The results of the investigation show that the new theoretical development can be utilised for a wide range of operating conditions and that it has been validated by comparing results with published literature of other workers and also with the results of experiments conducted in the laboratory.

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