STATIC AND DYNAMIC BEHAVIORS OF PURE SQUEEZE FILMS IN COUPLE STRESS FLUID-LUBRICATED SHORT JOURNAL BEARINGS

On the basis of microcontinuum theory, this paper theoretically invest igates the rheological effects of couple stress fluids on the static a nd dynamic behaviours of pure squeeze films in journal-bearing systems . The general modified Reynolds equation with no journal rotation is d erived by using the Stokes constitutive equations to account for the c ouple stress effects resulting from lubricants containing additives or suspended particles. The cases of short bearings under a constant app lied load and an alternating load are analysed. The solutions for film pressure in a closed form are shown, from which the squeeze film char acteristics are determined. According to the results evaluated the eff ects of couple stresses significantly increase the film pressure and t hen the load-carrying capacity is compared with the Newtonian lubrican t case. Under a cyclic load the couple stress effects provide a reduct ion in the velocity of the journal centre as well as an increase in th e minimum permissible height of the squeeze film. As a consequence, th e bearing with a couple stress fluid as the lubricant improves the squ eeze film characteristics and results in a longer bearing life.