Bending Fatigue Strength Studying Of Gear Tooth Under Random Loading

Gear is an important elements component in the mechanical products. Gear transmission is one of the most important mechanical transmission forms; it has broad power and speed ratio in scope, high transmission efficiency, compact structure and a series of advantages. Especially in recent years, with rapid technology development in automobile, aerospace, gear transmission became an extremely important form of mechanical transmission by people's concern.Fatigue failure is the main failure mode of the gear. The traditional gear transmission design method is fatigue strength design in constant amplitude based on the largest load in the actual gear transmission process. Generally, the impact of random vibration loads to the gear transmission was not considered. This method is mainly to satisfy the intensity, fatigue life, weight, volume and other conditions in static design; however, vibrations, high noise problems are appeared. In order to simultaneously guarantee light weight, low noise and other special design requirements, some parameters of the gear system and the static performance had to be designed to the limit near the brink of state failure. This brought capability prediction and life prediction inaccurate, and other related issues, so there will be huge losses based on one of the very small problems.Based on the analysis of the domestic and international theories, methods and general overview of the researches on the structural fatigue life prediction, the cumulative fatigue theory, fatigue load calculation methods and gear fatigue testing technologies are integrated used to theoretical analysis and experimental study the gear bending life prediction and design methods under the random loads conditions. My major work as following: Firstly,worked over the method of counting gear random fatigue load was different from traditional and more practical for gear; Secondly,the formula for calculating the equivalent load was derived according to the accumulated fatigue damage equivalent for random loads,work out the impact of the gear fatigue load distribution to the gear life, and the quantization numerical relation conclusions was given which provided guidance for the gear design under random loads; Finally, the bending fatigue testing method for the gear under random loads and the compilation method of load spectrum for testing were studied, and gear bending fatigue testing was carried out on the electro-hydraulic servo testing machine. The gear bending fatigue strength under random loads was concluded which was compared with the fatigue strength under constant amplitude loads. The theoretical result was proved validity and feasibility.In this Paper, the impact of the gear fatigue load distribution to the gear life was summarized by comprehensive study; the results will be in favor of the design and optimization for the gear under random loads.