Elastomer-lined bearings : an analysis of a heavily loaded cylinder sliding on a compliant layer
A theoretical model is developed which allows an expression for film thickness to be developed. The model approximates the film shape in the main load bearing region by a tilted pad and outside the main load bearing region by the equivalent dry contact solution. Two theories are developed, the modified and limited theories, the limited theory being valid for very small values for the slope of the tilted pad. Expressions for the frictional traction and starvation parameters are also developed for the two theories. The model used is applicable for intermediate and heavy loads. Values of film thickness obtained from the modified and limited theories are below those predicted by more rigorous theories (e.g., Herrebrugh), because the displacements due to the lubricant pressure in the inlet region are ignored for the former. The inlet ::one theory, which takes account of these displacements, produces a value for film thickness which is comparable to that obtained by Herrebrugh. The exit zone theory, which takes account of the additional displacements in the exit region, predicts a value for the ratio of minimum to central film thickness which is comparable to that obtained by Herrebrugh. Improved values for the frictional and starvation parameters are obtained using the inlet zone theory. Pressure curve and film thickness values are obtained from experimental rigs, for comparison with theory. The pressure rig utilises a pressure transducer for pressure measurement, whereas the film thickness rig utilises the principle of optical interferometry for film thickness measurement. It is concluded that the initial tilted pad model is a valid approximation to the shape of the loaded region, providing a conservative estimate of film thickness for the bearing designer. The use of an improved shape in the inlet and exit regions improves the agreement between experiment and theory.