Effect of Gear Design Variables on the Dynamic Stress of Multistage Gears

Abstract

This work presents a numerical model developed to simulate and optimize the dynamic stress of multistage spur gears. The model was developed by using the Lagrangian energy method and modified Heywood method, and applied to study the effect of three design variables on the dynamic stress on the gears. The first design variable considered was the module, and the results showed that increasing the module resulted to increased dynamic stress levels. The second design variable, pressure angle, had a strong effect on the stress levels on the pinion of a high reduction ratio gear pair. A pressure angle of 25^o resulted to lower stress levels for a pinion with 14 teeth than a pressure angle of 20^o. The third design variable, the contact ratio, had a very strong effect on bending stress levels. It was observed that increasing the contact ratio to 2.0 reduced dynamic stresses significantly. For the gear train design used in this study, a module of 2.5 and contact ratio of 2.0 for the various meshes was found to yield the lowest dynamic stress levels on the gears. The model can therefore be used as a tool for obtaining the optimum gear design parameters for optimal dynamic performance of a given multistage gear train.

Keywords: dynamic load, dynamic bending stress, gear design parameters, mesh stiffness, multistage gear train