Wear and Efficiency Mechanisms in Polyoxymethylene Spur Gears

Abstract

A method has been formulated to assess the running temperature of a polymer-steel gear pair under loaded operation. The slip-roll characteristic of an involute spur gear contact is used and forms the basis for this method. It derives a power loss at the contact interface that varies through the contact and is time averaged to provide an overall efficiency of the gears. This efficiency loss results in a rise in temperature at the contact between the teeth and in turn leads to a bulk temperature rise in the gears. This is assessed with finite element and analytical models to validate the predicted temperature rise against experimental data. Good correlation was found between the modelling techniques and the experimental results.A new mechanism of wear has also been identified for polymer gears. Themechanism is in the form of smear-shaped asperities approximately 20 휇m long from which fine particulates break away at the trailing edges during loaded operation of the gears, contributing to the bulk wear of material. The smear-shaped asperities and subsequent failure modes have been identified using scanning electron microscopy techniques. Two models are presented that are used to characterise and predict the phenomenon. One model characterises the failure mode properties of the smear-shaped asperities and is formulated by the inspection of the microstructure of the polymer material. The second model predicts the volume of material worn away and finds good agreement with experimental results. The predicted worn volume was 67 mg against 77mg measured.

Date of Award	26 Apr 2017
Original language	English
Awarding Institution	University of Bath
Sponsors	Rotork Controls Ltd
Supervisor	Patrick Keogh (Supervisor) & Sam Akehurst (Supervisor)