Boundary Lubrication Characteristics of Silica-Based Electro-Rheological Fluids

This experimental study presents friction and wear characteristics under boundary lubrication associated with silica-based ER (Electro-Rheological) fluids. Various types of base liquids (silicone oil, olive oil, transformer oil) and corresponding silica-based ER fluids are adopted as lubricants. As a first step, yield shear stresses of the ER fluids are measured as a function of imposed electric fields. Pin-on-disc wear testings are then performed with the lubricants by evaluating wear rates of the pin specimens. The governing relationship between the wear rate and the fielddependent yield stress is established for the application guideline of the ER fluids. Microscopic observations of worn surfaces of the pin specimens are also analyzed in order to validate the measured wear characteristics. In addition, friction coefficients of the ER fluids are experimentally evaluated with respect to normal loads.