The use of polymer gears in various applications has increased significantly in recent years, from the automotive industry to household appliances and industrial machinery. This is due to the favourable properties of polymer materials, including low weight, cost efficiency, low noise emissions and the ability to operate without the presence of external lubrication. However, the mechanical performance of polymer gears is lower compared to conventional metal gears, which leads to problems such as shorter service life and susceptibility to various types of failure. Due to thermal stability and elasticity differences, existing gear design standards tailored for metal gears are inadequate for polymer gear design. Although efforts have been made to develop guidelines specifically for polymer gears, challenges remain, particularly in accurately predicting fatigue life due to limited data and uncertainties in material behaviour. This thesis addresses key areas critical to understanding and improving the tooth root performance of polymer gears, focusing on tribological properties, geometry changes during operation, and operation in different environmental conditions. Through a comprehensive investigation of these factors, this thesis aims to improve the reliability and longevity of polymer gears by investigating the effect of tribological properties on tooth root fatigue failure and the possibilities for its prediction.
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