Analyzes the causes of fatigue fracture of mechanical gears

In fact, the so-called fatigue tooth breaking problem is that the mechanical gear breaks, and the whole spur gear will break according to the extension direction of the mechanical gear. Once the area of the mechanical gear is large, the end of the mechanical gear will break. Generally speaking, under the direct influence of the load, the mechanical helical gear is prone to tilt cracking.

The phenomenon of fatigue broken teeth is the generation of concave crack curve, which often occurs in the mechanical gear used for integral quenching. Or the cracking curve of concave step is produced, which is caused by surface oxidation treatment. Once these two kinds of fatigue tooth fracture problems appear, the staff can identify the specific location of the crack and observe the specific process of tooth fracture. The reason why the mechanical gear will appear fatigue broken tooth problem, the main influencing factor is the bearing pressure, the gear is in operation for a long time, if the bending stress at the tooth root exceeds the bearing capacity of the gear, then there will be serious fatigue, damage problems. In the long run, the root of the gear will be fatigue damaged because of the tension problem, and the crack will be lengthened or deepened with the increase of time until it is completely broken, and the mechanical equipment will no longer operate.

Specifically speaking, the problem of fatigue tooth fracture can be divided into two types, one is low cycle fatigue tooth fracture, the other is high cycle fatigue tooth fracture. Low cycle fatigue tooth fracture is very common, because the mechanical gear is always in the cycle work under the influence of bending stress, so it will appear fracture phenomenon. In addition, the mechanical gear in the process of bearing pressure, the internal gear has a certain degree of damage, in the process of bearing bending stress, the internal bearing capacity of the gear will gradually change, with the working time of the gear longer and longer, the elasticity of the gear raw materials will be worse and worse, and then there will be serious deformation problems, and gradually cracks, In the long run, serious low cycle fatigue fracture surface will be formed.

In a word, there are many factors that lead to the low cycle fatigue fracture of mechanical gears. The load of gears and the quality of mechanical facilities materials are important factors. The reason of high cycle fatigue gear fracture is that the number of stress cycles suffered by the gear is more than its actual bearing capacity, and the pressure at the root of the mechanical gear far exceeds its actual bearing capacity.

Generally speaking, this kind of problem will not appear in the early stage of work, but with the increase of the service time of the gear, the potential accumulated loss is more and more serious. Under the influence of long-term cyclic load, the mechanical gear will naturally be damaged due to the influence of stress concentration. If the number of stress cycles is too much, serious cracks will appear at the root of the mechanical gear, Then, the problem of high cycle fatigue tooth fracture appears. Specifically, if the whole mechanical working environment is relatively stable, the load stress changes little and the gear quality is high, then the mechanical gear will appear the problem of high cycle fatigue fracture in the process of long-term operation.