Wear Characteristics Under Boundary Lubrication Contacts in Phosphorated Starch-Based Electrorheological Fluid

Abstract

This experimental study examined wear characteristics under boundary lubrication contacts associated with electrorheological (ER) fluid composed of phosphorated starch particles and silicone oil. The ER fluids with starch phosphate are manufactured and adopted as lubricants. A pin-on-disc wear tester is then designed and constructed to evaluate wear rates of pin specimens. Specimens used for the experiments include steel, copper, and aluminum pins. The wear tests with the lubrication of ER fluid are experimentally performed under consideration of several operational factors such as normal load, sliding distance, and sliding speed as well as the specimen materials. Subsequently, microscopic surface and roughness changes of the worn surface of pin specimens are analyzed in order to validate the measured wear characteristics by using the scanning electron microscope (SEM) as well as surface profilometer. Friction coefficients of the ER fluid are also experimentally evaluated with respect to the sliding ranges. In addition, the chemical wear characteristics are investigated by using energy dispersive X-ray spectroscopy (EDS). In order to verify the effect of starch phosphate particles in ER fluid, the wear test results with ER fluid are compared with test results with only silicone oil, which is base carrier of ER fluid. The results clearly indicate that the phosphorated starch-based ER fluid tested shows the stabilized wear as well as friction characteristics after a certain period of operations but increased the wear rate as compared to the case with only silicone oil.