Optical Measurements of Rolling Friction Coefficients

Abstract: This thesis presents an optical method to measure the rolling friction coefficientsfor balls rolling freely on a cylindrical surface. Two different models of a ball rollingfreely on a cylindrical surface are established, one is an analytical model and the otheris a numerical model derived from Lagrange equation. The rolling friction coefficientsare evaluated from the position data of the steel balls. The positions data are retrievedfrom images recorded by a high-speed camera. The locating algorithms includingbackground subtraction and ball recognition are presented in detail. The rollingfriction coefficients between different diameter steel balls and a cylindrical aluminumsurface are measured. The angular positions of the balls are predicted by the solutionof the equation of motion (EOM), and good agreements are found between theexperimental and theoretical results. The values of rolling friction coefficientsbetween different diameter steel balls and a cylindrical aluminum surface areevaluated.