| Summary: | In this thesis a Finite Element Modelling (FEM) approach is proposed for modelling the visco-plastic creep effects that a PTFE-faced thrust bearing would undergo during normal operating conditions. A thermal elastic hydrodynamic lubrication (TEHL) model is developed, which uses the Reynolds equations for a fluid film, coupled with Hertzian contact theory and the energy equation to predict the pressure and film thickness on the PTFE face as well as the temperature and thickness of the fluid. These variables are then used with a Norton creep function to predict the secondary creep effects on the PTFE surface. This change in PTFE thickness due to visco-plastic effects are taken into account within the film thickness equations and the effects over a bearing’s operational life span studied. The Norton creep function is obtained from experimental creep results conducted on filled PTFE samples at the University of Leeds. This experimental method allowed for the displacement of the samples to be recorded over a 7 day test period at a representative range of pressure and temperature conditions and a Norton creep function to be obtained from the results. The Norton creep function was then included within the simulations to allow for the visco-plastic creep effects to be studied. Results obtained showed that whilst the secondary creep had a small effect on the pressure profile of the pad, the peak pressure was significantly affected during the duration of the pads operational life. It was concluded that this was due to the pad deformation changing, meaning a smaller peak pressure was observed, but the tilt angle did not change greatly, meaning the profile did not change. The pad and film thickness also changed as time passed, with the pad getting thinner in areas of high pressure and temperature, due to the secondary creep effects. It was also observed that the peak temperature of the pad also decreased as time passed, due to the film thickness increase in areas of high temperature.
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