An experimental study of ball-on-flat wear on a newly developed rotational tribometer

With the objective of experimentally correlating several wear-process parameters, accurately and continuously over the duration of a sliding test, this paper presents a novel test rig as well as experimental results obtained by it. The developed test rig is a rotational one with axes supported on aerostatic bearings. It enables online measurement of normal load, friction force, angular position and normal displacement with high accuracy. These measurements are supplemented by ante- and postmortem optical and tactile inspection of the wear samples to determine their geometrical evolution. A set of ball-on-disc experiments is performed, with ball materials being nylon, steel and ceramic, on hard steel disc material. The performed experiments correlate three process variables and parameters: normal load, wear volume and dissipated energy. The basic trends observed show that the relationship between those three variable are quasi linear, but generally with nonzero intercepts, corresponding to energy thresholds; except that of wear of alumina on steel.

► A correlation between the wear volume and the energy dissipated in the sliding contact is sought. We design and build a test setup and observe experimentally a linear trend of the wear volume as function of the dissipated energy, however, with a shift along the energy abscissa, which can be explained in accordance with the concept of threshold energy needed to initiate wear.
► This trend is investigated for steel, alumina and nylon sliding on steel. Steel and nylon show qualitatively similar behaviour, which is quasi-linear in normal load and dissipated energy. Alumina shows saturation in both variables, presumably owing to the presence of abrasive wear.
► These results are obtained on a specially designed rotational, pin-on-disc tribometer, equipped with air bearings. It enables the online measurement of the normal load, the friction force, the angular position and the normal displacement, simultaneously. Optical inspection and tactile profilometry are also applied to the ante-mortem and post-mortem samples.