Evaluation Method Research Of Fatigue Life For Spur Gears In Helicopter Main Reducer

:Evaluation of fatigue life is an important part in helicopter research, and it’s also a key technical indicator in reliability check for transmission system. The key and important parts in transmission system with high cycle fatigue life, especially the spur gears, have characteristics such as single channel force, complicated loads and fickle flight condition, these characteristics would cause disastrous accident once fatigue failures appeared. Therefore, it’s of great significance to discuss fatigue life for spur gears in helicopter main reducer.Firstly, two evaluation method of fatigue life for gears were studied. One method was based on S-N curve, and another method was based on Lundberg-Palmgren theory combined with Hertz contact theory, these two methods considered that fatigue life was related to contact stress. Meanwhile, contact stress and maximum Hertz contact stress were respectively obtained by American standard ANSI/AGMA2001-D04and ANSYS software.Secondly, contact fatigue test for spur gears were completed to improve these two methods, and a method based on tooth surface image to judge whether the gears were failure or not was improved. Based on the test data, influence factors of fatigue life were studied and the expressions of fatigue life were obtained. Through the experiment, these two methods were proved to be accurate, and contrastive analysis for these two methods was accomplished.Finally, four programs were completed, these programs respectively focused on solution of contact stress, evaluation based on S-N curve, evaluation based on Lundberg-Palmgren theory and solution of pitting image, and thus could simplify some work in evaluation of fatigue life.