Experimental evidence of cavitational effects in a Rayleigh step slider

Abstract

The objective of this article is the study of the load-carrying capacity of a Rayleigh step slider (RSS) for both direct motion (+RSS – which generates lifting effects) and reverse motion (−RSS – which generates suction or cavitational effects). Normal force was measured on a pin-on-disc test rig, with two lubricants (SAE-20 W-50 oil and glycerin) at four speeds and three values of film thickness. During reverse motion (−RSS), cavitational effects have been observed for some test cases. It is supposed that surface tension influences the appearance of cavitational effects, and a modified capillary number, Ca⁺, is proposed as indicator of cavitation inception. Close-up views taken near the trailing edge of the pin show the occurrence of several streamers, typical for cavitational effects, only when Ca⁺ > 2. Numerical simulation as well as approximate analytical models are presented for both directions of motion. The comparison of predicted theoretical results with the experimental data is satisfactory.

Keywords

hydrodynamic lubrication step slider experiment cavitation capillary number

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