Stress Evaluation at the Root Fillet in Cylindrical Gear: A Semi-Analytical Approach Compared With Standard and Numerical Methods

The evaluation of the fatigue life in gears due to bending loads is still an important task due to the necessity to increment the power density of the gearboxes but reducing the weight. The usage of Finite Element Method allows to properly evaluate the stress distribution in the root fillet, also taking into account the actual contact ratio and the load sharing factor. However, such procedure is time consuming because it requires a final geometry of the gear pair and long time for preparing and solving the model. On the other hand, the standards provide a quick and precautionary insight of gears, but loosing info regarding the actual force sharing trend among teeth. The aim of this paper is suggesting a strategy for evaluating stress and fatigue behavior of the gear during the predesign phase, where the geometry is not yet finalized, but the choices are easier and less costly. The paper analyzes the ISO 6336 standard in the 2019 version, compares it to the FEM solution and proposes a semi-analytical method that maintains a good accuracy and a low computational cost. The proposed strategy also offers the possibility to correctly estimate the gear performance, because the trend of stress can be easily considered along the meshing cycle.