Static and dynamic behaviours of pure squeeze films in couple stress fluid-lubricated short journal bearings

Abstract

On the basis of microcontinuum theory, this paper theoretically investigates the rheological effects of couple stress fluids on the static and dynamic behaviours of pure squeeze films in journal-bearing systems. The general modified Reynolds equation with no journal rotation is derived by using the Stokes constitutive equations to account for the couple stress effects resulting from lubricants containing additives or suspended particles. The cases of short bearings under a constant applied load and an alternating load are analysed. The solutions for film pressure in a closed form are shown, from which the squeeze film characteristics are determined. According to the results evaluated, the effects of couple stresses significantly increase the film pressure and then the load-carrying capacity is compared with the Newtonian lubricant case. Under a cyclic load the couple stress effects provide a reduction in the velocity of the journal centre as well as an increase in the minimum permissible height of the squeeze film. As a consequence, the bearing with a couple stress fluid as the lubricant improves the squeeze film characteristics and results in a longer bearing life.