Analytical treatment of uncertainties for a macroscopic tribology instrumentation

In tribology, friction coefficient and wear rate are usually determined experimentally. The present work is aimed at investigating the measuring uncertainties associated with the evaluation of these two parameters. In particular, a standard pin-on-disk tribometer, having two pins constrained to a counterface, has been used. Varying normal load, sliding distance and test duration, a total of twenty tests have been carried out. Environmental temperature and relative humidity have been maintained constant. After the tests, a stylus profilometer has been used to acquire the wear scar profiles on the cross-sections of the disks. The wear rates have been subsequently calculated by measuring the area of the wear track cross-sections and evaluating an average wear volume. The experimental results show that the load measurement uncertainty strongly affects the evaluation of both friction coefficient and wear rate. The information obtained is useful to optimise the experimental apparatus and/or to develop suitable procedures aimed at reducing measurement uncertainties.