ACCELERATED LIFETIME TESTING OF REINFORCED POLYMER GEARS

Abstract

The main advantages of polymer gears in comparison to metal gears are low manufacturing costs for mass production, vibration damping and no need for lubricant. In the literature and guidelines, the allowable gear endurance limits for bending and contact stresses are mainly given for polyamides (PA) and polyacetals (POM). The large number of suitable polymer gear materials is available, but the standards offer little support for the lifetime calculations of polymer gears from other materials. Therefore testing of gear geometry and materials combinations cannot be avoided in the design of an optimal gear drive. However, gear testing is very time consuming and expensive, especially when testing several different material combinations at different testing conditions. By applying the accelerated testing procedure gear test time and costs can decrease significantly. Determination of the gear temperature during meshing is needed for the precise calculation of plastic gears. The presented temperature calculation model is using the Hachmann–Strickle temperature model, however with corrected and improved input parameters, which were determined from the test results. Accelerated tests were conducted on different combinations of reinforced and unreinforced commercially available materials: PA6, PA66, POM and PPS. Glass and carbon fiber were used for reinforcement. The research goal was characterization of different material pairs with friction coefficient, time strength, wear and failure mechanism in the relation to speed of rotation and load level. (Less)