Effects of couple stresses on the lubrication of finite journal bearings

Based on the microcontinuum theory, this paper investigates theoretically the rheological effects of couple stress fluids on the lubrication performance of finite journal bearings. To take into account the couple stress effects resulting from lubricant blended with additives, the modified Reynolds equation is derived from the Stokes constitutive equations. With zero pressure-gradient conditions for the film extent, the film pressure is solved numerically using the conjugate gradient method of iteration. Various bearing characteristics are then calculated. According to the results predicted, the presence of couple stresses has a significant affect on the static characteristics of finite journal bearings. Compared with the Newtonian-lubricant case, the effects of couple stresses enhance the load-carrying capacity, as well as reduce the friction parameter and the attitude angle. Overall, the couple stress effects improve the lubrication characteristics of the journal-bearing system. These results agree qualitatively with experimental works. (C) 1997 Elsevier Science S.A.