Rim Stress Analysis of Epicyclic Gearbox

Abstract

The design procedures developed for external gear pairs are often used for planetary gears. The gear rims of external as well as particularly ring gear are thin in case of planetary gear box. The thin rims are preferred because of cost reduction and weight reduction also. Therefore rim stresses become important for these types of gear boxes. In this paper rim stress for a ring gear are estimated by using curved beam theory. The bending stresses and the stresses across the thickness of ring gear are also estimated by Finite element Method (FEM). The experimental setup consists of planetary gear box with strain gauges mounted on the rim of ring gear. The stress measurement is done under static loading conditions, for which output shaft was locked with suitable locking arrangement. The input torque was provided with a lever attached to the input shaft. The experimental stresses on the rim surface for different planet positions were compared with FEM results. The stresses across the rim thickness are estimated with FEM and are in good agreement with the theoretical. The effect of angular position of planet on the root stress of ring gear is evaluated. The stress distribution along the length of rim between two fixing bolts is estimated by FEM.