Numerous concepts, national and commercial design standards developed and proved for metallic gears, now are being migrated over to polymer gears. However, it is uncertain whether the same procedures should apply and there is only limited data available to attempt a validation. Since wide mechanical and thermal properties’ discrepancies exist between metals and polymers, it is essential to develop and establish their individual investigation methods and science of design. The work presented in this thesis endeavours to bridge this gap between practical application and theory, through exploring advances in fundamental experimental investigation approaches and providing effective test data. New studies on wear and failure mechanisms, in addition to adopting the prevailing methods (i.e. SEM examining worn tooth surfaces), and inspecting wear debris are proposed and employed. Schemes are proposed for measuring the temperatures and velocities in the airflow surrounding the operating gears and gear bulk temperatures. Their use adds to the work for predicting surface temperatures of polymer gears. Deliberate misalignment is introduced to investigate. Wear and failure mechanisms of polyacetal gears at various loads and a speed of 1000 rpm are studied. Various regimes of wear debris and topographies of worn tooth surfaces are presented. The dynamic evolutions of wear, wear rate and the temperatures of airflow and the tooth body (bulk) are presented. It is found that transition temperatures are more reliable for assessing the gear wear compared to transition torques. Gross misalignment effects on the performance of polyacetal gears are investigated. Strikingly distinct topographies of worn tooth surfaces and regimes of wear debris are presented. It is indicated that polyacetal gears are most sensitive to pitch misalignment. Micro-cracks are noted near pitch points and tooth roots. Aerodynamic characteristics of operating gears are studied and an improved model is proposed. On the basis of it, methods for improving the durability of polyacetal gears are proposed. Further investigations on aerodynamics, thermal-mechanism and misalignment are recommended to gain a better temperature and wear prediction, and understanding of misalignment.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:737718 |
| Date | January 2017 |
| Creators | Hu, Zedong |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/99346/ |
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