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Title: The mechanical contact behaviour and tribology of polymer gears
Author: Alharbi, Khalid Abdulkhaliq M.
ISNI:       0000 0004 7425 6236
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2018
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Interest in using polymer gears has been growing dramatically in the last decade. Increasing understanding of their working behaviour has improved appreciation of their advantages compared to their limitations when selecting appropriate applications. However, restricted knowledge still leaves many unfulfilled areas that might benefit from their valuable advantages and control of their limitations, for example, in replacing. their metallic counterparts in more applications. Given their very different materials properties, it is important to develop bespoke design and rating methods for polymer gears, with properly validated rules, that are not mere modifications to metallic gearing rating methods. A major aim of this thesis is to provide a new deeper understanding for use when designing and rating some technologically important types of polymer gears for wider applications. Having identified an important research gap in polymer gearing theory and practice, this thesis covers mostly experimental studies involving continuously monitored wear and wear rate and microscopic evaluation of underlying tribologies. It examines the behaviour of polymer gears made of acetal, nylon (moulded and machine-cut) and polycarbonate, all common gearing materials, during and after running under different physically realistic conditions. Some modifications to test rigs uniquely designed to operate at a continually constant load enable study of surface thermal behaviour under dry and lubricated conditions and with simulations of moderate gear misalignments. In dry-running cases, gear load capacity and wear behaviour of different polymers and variations in underlying tribology all presented important relations between the gear tooth wear rate, the applied load and the tooth surface temperature. Quite similar patterns were seen under oil lubricated conditions. Typically, though, there was a nearly three-fold improvement in gear load capacity, the wear rate and gear tooth surface temperature were decreased, and SEM showed some changes in surface tribology. Finally, deliberately introduced angular misalignments between gear pairs indicated a reasonable tolerance of small but practical levels, with different tribological behaviours between the left and right sides of the tooth surfaces. A severe increase in wear rate and tooth failure arose from misalignments above 0.8ο yaw angle and 0.4ο pitch angle. After a unifying discussion, conclusions are drawn and further work is proposed for extended studies over different parameter ranges.
Supervisor: Not available Sponsor: Jāmiʻat Umm al-Qurá
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TJ Mechanical engineering and machinery