Effect of track geometry on the measurement uncertainty of wear in pin-on-disc tribological test

Wear is connected to friction and hence affects energy efficiency and the environmental footprint of the process. The precise evaluation of wear damage will gain further relevance because it is a core input for developing prediction models of mechanical behaviour of materials, to be applied in the design stage of components and systems, and in the optimisation of new manufacturing processes and innovative materials, within the framework of Industry 4.0 and circular economy. Given the complexity of wear phenomenon, simplified wear tests are required; amongst these, pin-on-disc is a widespread test. It consists in sliding a pin against a disc either according to a circular path or along a linear alternate motion, to generate a track, whose volume is the characterisation target. Its characterisation standards rely upon gravimetric and volumetric method, which have several limitations, though. The former is inadequate for low-wear application and multi-material and multi-phase components, due to the difficulty in locally estimating material density. The latter, requiring profilometric measurements, does not suffer from these limitations; however, profilometric measurements are superseded by high-resolution and information-rich inspection techniques based on surface topography measurement, with respect to whom are less robust and representative. The profilometric method relies on a-priory defined track geometry; despite it is largely exploited, the effect of this approximation is unreported within a rigorous metrological framework. This work aims at assessing the effect of the track geometry on the accuracy and precision of the volumetric method, both according to standardised and surface topography approaches, within the current standards for topography measuring instruments based on metrological characteristics. This provides insights in the performance comparison of standard and non-standard volumetric methods in quantifying wear in pin-on-disc testing. The results will support the standardisation of topography-based method by providing users with confidence in their use and establishing traceability for this tribological test.