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This paper presents the tribometric characteristics analysis of a journal bearing system lubricated with ferrofluid (FF) considering different shaft materials. Two magnetically permeable materials namely, EN-19 and mild steel were used to manufacture the journal. These journals were made magnetic by inserting neodymium magnet inside. It was seen that the magnetic shaft made from EN-19 offered a better dimensional accuracy in comparison with the magnetic shaft made from mild steel. Thus, magnetic shaft made from EN-19 was used in a brass bearing to evaluate various tribometric characteristics namely, fluid film pressure, fluid temperature rise, bearing vibrations, friction torque and wear at various conditions. The experimental results showed that the maximum pressure enhanced up to 84% in the case of FF based bearing system in comparison with conventional lubricant based system. Also, the film pressure was measured for newly acquired FF and the three years old FF to check the stability of the FF. It was found that almost no change in the pressure profile was observed. Further, the temperature rise was found to be less in FF based system while marginal difference in damping characteristic was observed. Moreover, tribometric characteristics such as friction and wear were also investigated and compared between FF based and oil based bearing system. A significant drop in friction torque was found in the case of FF based system. In addition, the wear loss due to the machine starts and stops was measured in lubricated condition for several systems using weight loss and stylus method. However, wear loss was found to be marginally increased in the FF based system, in comparison with the low viscous conventional fluid based system. It has been clearly established that the FF based system presented here, may turn out to be a better option from efficiency and stable system point of view. |
