Method for measuring transient friction coefficients for rubber wiper blades on glass surface

A method for measuring the coefficient of friction between sliding solid bodies has been developed. In the proposed method, both frictional and normal forces are measured as inertial forces acting on masses. Two pneumatic linear bearings, one placed horizontally and the other vertically, are used to realize a linear motion with a sufficiently small friction acting on the masses, i.e., the moving parts of the linear bearings. The inertial force acting on each mass is calculated from the velocity of the mass; this velocity is determined with a high accuracy by measuring the Doppler shift frequency of a laser light beam that is reflected off the mass using an optical interferometer. The performance of the proposed method is demonstrated by measuring the coefficient of friction between a car wiper blade and a glass surface.