| dc.description.abstract | Previous investigations of rubber friction have focused around the automotive/motorsport industry, where contact pressure levels are typically less than 1 MPa and the sliding velocity is a key variable. The current project endeavours to better understand what controls the level of rubber friction at higher pressure levels (above 10 MPa) and at higher temperatures (>100°C). The thesis outlines the design of a new rig. An explanation of how the apparatus was used to measure the sliding friction is described. The rubber materials characterised in this report were all commercially available compounds, typical of those used in the oilfield. The rubber compounds were characterised for their mechanical and thermal properties to help characterise and model their behaviour. The coefficient of friction was derived by dividing the measured friction force by the normal force, which was determined using a Finite Element Analysis (FEA) modelling approach. Testing was carried out at three different temperatures, with two types of materials in two different liquid environments. From these tests, the frictional force at the interface between the metal surface and the rubber was characterised at different sliding speeds. Different types of surface analysis techniques were used to characterise the sliding surface. The surface analysis was then related through the sliding velocity to a characteristic frequency of deformation during sliding of the rubber seals. Using independently measured dynamical mechanical analysis (DMA) data, the frictional behaviour was related to the viscoelastic properties of the rubber. Using the experimental friction results and characterisation techniques, different friction models from the literature were tested against the measured data sets to observe which were best suited to this type of application. The final chapter outlines the best way to model rubber surface interactions in FEA under these demanding conditions and compares the results of this investigation with the recognised industry standards. | en_US |
