The influence of pin inclination on frictional behaviour in pin-on-disc sliding and its implications for test reliability

The pin-on-disc test is a widely employed method for investigating the friction and wear performance of materials in conformal contact. In a typical pin-on-disc system, self-aligning pin holders are frequently utilized to ensure proper surface contact. This study reveals that in such a setup, pin inclination has a significant impact on test reliability, particularly under oil-lubricated conditions, which may overweight the influence of other parameters such as roughness or texture elements. Utilizing in-situ measurements, we captured the dynamic changes in pin inclination during rotational sliding. Our findings indicate that the pin inclination varies with sliding speed, showing a pitch angle difference of approximately 0.01 degrees degrees as the speed decreases from 2 m/s to 0.04 m/s in our test setup. Importantly, a robust correlation was identified between the friction coefficient and pin inclination, which is supported by the numerical investigation. This study underscores concerns regarding the test reliability of pin-on-disc tribometers, prompting a reconsideration of the assumptions associated with self-aligning pin holders in such experimental configurations.