Experimental Investigation of Coefficient of Friction During the Friction Stir Processing of Aluminum

There is a lack in understanding of the frictional contact condition during friction stir processes. High temperature, force and work material adhesion to and from the tool make the coefficient of friction difficult to measure. In this study, an experiment was set up to simultaneously measure the temperature and normal and frictional forces between a rotating tool and a stationary workpiece at steady state conditions. The coefficient of friction was measured for increasing temperature. A simple model was created to convert the thermocouple temperature measurement to the temperature at the point of contact between the tool and workpiece. It was found that the coefficient of friction had a decreasing trend as temperature approached the solidus temperature of the work material. The results and analysis of the experiments are presented.