Accuracy of Stanton’s Formula Used for the Data Processing of a Pendulum Friction Test

Abstract

Pendulum friction-tester is specifically useful for experiments in biotribological field because that is good at the measure on circular sliding surfaces, like as synovial joints, joint prostheses, eye balls, or contact lenses. Stanton’s formula has been generally used for the data processing as the calculation of friction coefficient from the amplitude decay during a pendulum libration. Because Stanton used the balance of moment to analyze the pendulum motion, his analysis must inevitably include an approximation of sin θ as angle θ. However, the error in the formula has not been evaluated because the strict analysis was thought to be impossible. In the present study, the strict analysis was clarified by energy balance in a pendulum. As the result, error in Stanton’s formula was able to be evaluated.