Analysis of Measurement Inaccuracy in Superlubricity Tests

Although investigations on superlubricity are increasing, the corresponding measurement errors, which have a great effect on the measured friction coefficient, have not been widely discussed. The present article analyzes the origin of friction measurement errors in a rotating ball-on-flat apparatus and shows that these errors play an important role in the relationship between the measured and real friction coefficient. Based on the analysis, two methods were proposed to eliminate the main measurement error. One is obtaining the same friction coefficients in two reverse sliding directions by adjusting the level of the substrate (rotating plane) and the other is averaging the measured friction coefficients in two reverse sliding directions. The designed experiments proved the effectiveness of the two methods in eliminating the measurement error. Such methods are also effective for investigations on superlubricity.