Gearboxes that employ polymer gears are being used in an ever-increasing number of different applications. However, polymer-gear design suffers from a lack of understanding of their tribological ...behaviour under controlled – but at the same time realistic – conditions. One of the factors that is often overlooked in model tribological tests is the effect of the slide-to-roll ratio (SRR), which is different in gear meshing and conventionally used model tribological experiments with pure sliding. In this study, we analyse the wear mechanisms and wear coefficients, as well as the friction, in very common gear pairs of non-lubricated POM/steel contacts, but at different SRRs (25–150%) and at two controlled temperatures (50 and 80 °C). The load was also varied (8 and 45 N). The results show that tests at 50 °C in SRR-variable model tribotests can predict the SRR-dependent wear mechanisms along the meshing path (positions A–E) in real gears, while the 80 °C tests are too severe, leading to thermal overload. An about 10-times-larger wear coefficient, compared to the gear tests, was measured during our SRR-variable tests, which is a better estimation compared to the common pin-on-disc test with 2–4 orders-of-magnitude deviation. Furthermore, based on an accurate simulation of the friction behaviour in model tribotests, compared to gear tests, an empirical model based on tribological tests with a variable SRR was developed that predicts the coefficient of friction along the meshing contact line in real-scale gears with a 3% deviation. This study shows that the SRR- and temperature-controlled model tribological tests are relevant for understanding the real-scale polymer gears’ tribological behaviour and mechanisms and furthermore they generate predictive, empirical results.
•Tribology of non-lubricated POM/steel ball-on-disc contact at different SRRs, loads and surface constant temperatures.•Wear behaviour of polymer gears in contact with steel pinon under similar conditions as SRR-variable model tribotests.•Tests at 50 °C in SRR-variable model tribotests can predict the wear behaviour in gears while the 80 °C tests are too severe.•An empirical model was developed to predict the friction coefficient along the meshing contact line in real-scale gears.
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