A theoretical study of the effect of the viscosity variation on the squeeze film performance of a short journal bearing operating with micropolar fluid is presented. The modified Reynolds equation accounting for the viscosity variation in micropolar fluid is mathematically derived. To obtain a closed form solution, the short bearing approximation under constant load is considered. The modified Reynolds equation is solved for the fluid film pressure and then the bearing characteristics, such as obtaining the load carrying capacity and the squeeze film time. According to the results evaluated, the micropolar fluid as a lubricant improves the squeeze film characteristics and results in a longer bearing life, whereas the viscosity variation factor decreases the load carrying capacity and squeezes film time. The result is compared with the corresponding Newtonian case. 1. Introduction The application of squeeze film action is commonly seen in gyroscopes, gears, aircraft engines, automotive engines, and the mechanics of synovial joints in human being and animals. The squeeze film behaviour arises from the phenomenon of two lubricated surfaces approaching each other with a normal viscosity. Because of the viscous lubricant present between the two surfaces, it takes certain time for these to come into contact. Since the viscous lubricant has a resistance to extrusion, a pressure is built up during that interval, and the lubricant film then supports the load. If the applied load acts for a short enough time, it may happen that the two lubricated surfaces will not meet at all. Therefore, the analysis of squeeze film action focuses on the load carrying and rate of approach. The theory of micropolar fluids introduced by Eringen  deals with a class of fluid which exhibits certain microscopic effects arising from the local structures and micromotion of fluid elements. These fluids can support stress moments and body moments and are influenced by the spin inertia. A subclass of these fluids is the micropolar fluids which exhibit the microrotational effects and microrotational inertia. Eringen’s micropolar fluid theory defines the rotation vector called microrotation vector setting up of stress-strain rate constitutive equations. The study of micropolar fluids has received considerable attention due to their applications in a number of processes that occur in industries such as extrusion of polymer fluids, solidification of liquid crystal, cooling of metallic plate in a bath, animal blood exotic lubricants, and colloidal and suspension solution. In the study of all
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