This paper described unique hysteresis phenomena that appear in the hydrodynamic lubrication properties of dimpled thrust bearings. A seal-type thrust bearing specimen was textured with dimples. The load-carrying capacity and frictional torque were measured with a constant film thickness and compared to those of a dimple-free specimen. For examining the size of cavitation bubbles that occurred in various conditions, the lubricating area was observed during experiments. The used dimpled specimen produced the load-carrying capacity, and it exhibited an interesting hysteresis phenomenon, the difference in the values in the increasing and decreasing processes of rotational speed. The visualization test results revealed that the size of cavitation bubbles occurring within the dimples strongly affected this phenomenon. In addition, the dimpled specimen was able to reduce the frictional torque compared to the dimple-free specimen. However, the frictional torque did not show the hysteresis loop similar to that shown in the load-carrying capacity.

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This study involved an experimental investigation of the hydrodynamic lubrication performance of dimpled seal-like thrust bearings. Circular dimples were created on lubricating surfaces and the hydrodynamic effects were evaluated. The load-carrying capacity and frictional torque were measured under a constant film thickness. The lubricating surface was observed to make clear the effect of the cavitation area on the load-carrying capacity and the frictional torque. Dimpled specimen produced the load-carrying capacity and it showed a signature hysteresis phenomenon. Cavitation strongly affected the phenomenon. In addition, the dimpled specimen could reduce the frictional torque compared with the plane (dimple-free) specimen. However, the hysteresis phenomenon of the frictional torque was not clear compared with that of the load-carrying capacity.