Wear testing and measurement techniques for polymer composite gears

Injection-moulded composite gears using fibre-reinforced thermoplastics oft en exhibit increased performance compared with those made from unreinforced polymers. In general, materials are chosen on cost or simple performance g rounds (such as, nominal flexural modulus or heat deflection temperature). Aspects of the performance of polymeric gears have been studied by a number of workers and efforts have been made to simulate the contact conditions d uring gear running. However, until now the wear performance of gears made f rom polymer matrix composites has not been studied systematically. While su ch materials have been studied using pin-on-disc or twin disc roll/slide we ar techniques, no attempt has ever been made to directly compare the result s from such studies with those from gear tests. This paper attempts to expl ain the comparative methods of measurement of various polymer matrix compos ite gear materials and to relate their performance to results obtained in c ontact simulation experiments by other workers. Methods of wear testing are compared including direct gear testing and disc testing, together with electronic (displacement) measurement, weight loss and direct measurement. A new method of characterising the wear of gears is presented, which relates actual contact conditions and (year tooth wear. T his co-ordinate measurement technique provides wear rates as a function of roll angle, and hence load, sliding speed and slip ratio. It allows compari sons between gear tests and a simpler test configuration, the twin disc rol l/slide test. The conclusions reached have interesting commercial implicati ons for the producers and end users of polymer composite gears and for thos e involved in testing them. (C) 2001 Elsevier Science B.V. All rights reser ved.