Negative Pressure in the Oil Film of Journal Bearing : 2nd Report, Conditions for the Development of Negative Pressure and its Value

Abstract

Taking into account the surface dilatational viscosity κ, influences of eccentricity ε and 8 parameters on the limit of development and on the value of negative pressure including tensile stress are studied : When κ is taken into account, negative pressure develops in a wider range of ε and parameters, and its maximum value tends to be larger. Whether κ is taken into account or not, the larger ε is, the greater is the number of parameters, which limit the negative pressure development and therefore the more hardly develops the negative pressure, but the larger is the developed negative pressure. The oil film ruptures then, when the force of κ and surface tension cannot suppress the bubble expansion. When ε, oil viscosity and initial vapor radius are small and κ is large, negative pressure in the oil film can increase with increasing rotational speed, because the effect of κ suppresses the bubble expansion, as long as the assumptions made in the bubble calculation hold.