Theoretical and experimental investigation of wear in internal gears

Internal gears are commonly used in automotive and aeronautic industries as external sun gears of planetary mechanisms. Internal gears have some advantages such as low sliding velocities, low contact stresses, high contact ratios compared with external gears. Therefore, manufacturing is more difficult than external gears. For this reason, it is necessary to determine the working conditions of internal gears carefully. For that purpose, wear in internal gears is investigated theoretically by adapting Archard's wear equation to internal gears and a MATLAB® programme is written to solve this modified equation. The aim is to determine the wear values in different conditions by using this modified equation. In addition, a fatigue and wear test equipment is designed and manufactured which is similar to FZG (Forschungsstelle für Zahnrader und Getreibbau) closed circuit power circulation system in working principle to investigate wear in internal gears experimentally. Internal spur gears which are manufactured from St50 are used in the experiments with different torques and motor speeds. Wear is determined that occurs in tooth profiles of internal gears for different load cycles. It is seen that the results obtained from theoretical and experimental studies are compatible.