SIZE EFFECTS IN TILTING PAD THRUST-BEARINGS

For a pad with any given support system, the design can be scaled up directly without size effects provided only elastic distortion is considered. However, thermal distortion tends to increase directly with bearing size. By considering a wide size range of geometrically similar bearings with disc supports, it is shown that the maximum obtainable unit loading decreases approximately exponentially with size. Large bearings are particularly prone to failure by a thermal ratchetting process. This effect is far less marked in small bearings where the maximum load is more likely to be limited by film thickness or mechanical strength. Methods of controlling the effects of thermal distortion are discussed.