Flank load carrying capacity of oil-lubricated high performance plastic gears: Analysis of the pitting development in back-to-back tests

Plastic gears for power transmitting gearboxes are gaining more and more importance. Operation under oil-lubricated conditions and the use of high-performance materials allow significant increases of the transmitted power compared to dry running systems. Extensive experimental investigations on back-to-back test rigs with PEEK spur gears show that typical failure modes such as wear and thermal damages can be prevented under sufficient lubricating conditions. However, fatigue damages such as pitting on the active flank become more relevant. Current state of the art calculation methods like VDI 2736 do not contain strength numbers for PEEK materials. Therefore, experimental investigations on the pitting damage development and the resulting flank load carrying capacity of PEEK spur gears have been started and first results were evaluated.