An investigation on the wear behaviour of dissimilar polymer gear engagements

Following an interesting observation reported in the Wear of Materials 2009 by the present authors [1], the current paper will present an extensive investigation of dissimilar polymer gear contact, friction and wear behaviour. The unique polymer gear test rig employed will be briefly introduced. The most interesting observation from the experimental work is the significantly different wear behaviour when running acetal against nylon gears, especially the low wear rate when the acetal gear is the driver. To understand the interesting behaviour, detailed modelling work has been carried out to investigate the mechanisms of dissimilar gear engagements as well as which one is the driver. The advanced non-linear finite element method has been employed to simulate the gear tooth contact. It has been found that the gear contact force during the access process is higher than that in the recess process. Further work has been carried out on the high performance PEEK gear contacts, i.e. PEEK against steel, steel against PEEK and PEEK against PEEK. To improve the high friction and wear of the gear tip, a micron geometry modification method, tip relief, has been employed and significant frictional contact force reduction has been achieved.