Studies on tribology.
Bottom Line: Oil whip is one of such vibrations due to oil film action of journal bearing.Some mechanisms of wear are introduced for better understanding of tribo-layer.In the last part of this paper, the mechanisms of generating static friction are shown for the cases of plastic contact and elastic contact, which is the base for understanding the mechanism of initiation of macroscopic sliding.
Affiliation: Kanazawa Institute of Technology, Tokyo, Japan.
In high speed rotating machines such as turbines and generators, vibrations of a rotating shaft often hinder the smooth operation of the machine or even cause failure. Oil whip is one of such vibrations due to oil film action of journal bearing. Its mechanism and preventive method is explained and proposed in this paper. Further theoretical and experimental analyses are made for considering heat generation and temperature rise in hydrodynamic lubrication. The usefulness of the lubrication theory based on the k-epsilon model is also shown for bearings with high eccentricity ratios. In the latter half of this paper, water lubrication, nitrogen gas lubrication and tribo-coated indium lubrication are shown as new promising methods, and their mechanisms are discussed and the importance of tribo-layer is explained. Some mechanisms of wear are introduced for better understanding of tribo-layer. In the last part of this paper, the mechanisms of generating static friction are shown for the cases of plastic contact and elastic contact, which is the base for understanding the mechanism of initiation of macroscopic sliding.
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Mentions: As shown in Fig. 34, In coating by vapor deposition only is bonded to the surface of SUS440C disk very weakly and quickly removed from the surface after about 500 cycles of sliding against a Si3N4 pin and gives high friction. In tribo-coating of In, on the other hand, some surface layer so called tribo-layer is formed on the wear surface of Si3N4 pin after sliding against SUS440C disk as shown by the SEM image in Fig. 36 (a1). However the chemical analysis on the same surface by EDX does not show the clear uniform existence of In as shown in Fig. 36 (a2). Some small amount of In is detected only along the periphery at the contact entrance. Figure 36 (b1) shows for comparison the similar SEM image of tribo-layer observed on the wear surface of Si3N4 pin after sliding. Analysis on its surface by EDX shows rich existence of In in this case as shown in Fig. 36 (b2). The friction coefficient is around 0.02 with the tribo-layer shown by Fig. 36 (a1) and around 0.07 with that by Fig. 36 (b1), which means that a surface layer of In only is not sufficient to give friction coefficient around 0.02.71)