Kinetic friction coefficient modeling and uncertainty measurement evaluation for a journal bearing test apparatus

This paper presents a detailed assessment of a tribometer that was developed for dry journal bearing tests, with the aim of modeling the kinetic friction coefficient and determining its uncertainty. In this tribometer, the normal force is provided by a deadweight system and the friction force is measured in a load cell. The kinetic friction coefficient model was developed, as the ratio between friction force and normal force, and demanded free body diagrams evaluation to identify how forces act during the tribometer's operation. It was found that the load cell uncertainty varied over the tribometer's operating range (from 2.2 to 5.7 gf) and the last digit fluctuation error (a kind of statistical error) dominates the behavior of the load cell total standard uncertainty (similar to 98.8% on average). The kinetic friction coefficient uncertainty was obtained (as 0.002) and its determination was made by an error propagation analysis of the model itself. (C) 2020 Elsevier Ltd. All rights reserved.