Initiation and growth of gaseous cavity in concentrated contact in various surrounding gases

This paper describes an experimental study on the initiation and growth of gaseous cavity in EHL. Lubricated point contact sliding tests and separating tests were conducted in various different gas environments. Gases used were air, helium, argon and carbon dioxide. In the sliding tests, length of a cavity rapidly increased with time in the initial stage after its generation, and the speed of the increase was the same in all of the gases. The cavity length gradually increased after that at different speeds depending on the solubility of gas in the lubricant as reported in the previous study. In the separating test, changes in the size and the shape of the cavities were the same for all of the gases. This implied that the growth of cavity in the initial stage did not depend on dissolved gas in the lubricant. It is shown by a simple numerical analysis that the initial growth of the cavity depends on the rapid evolution of negative pressure at the outlet of the conjunction.