Michael E. McCune

Evaluation of Ring Gear Tooth Stress

To optimize the operating speeds of the low spool of a gas turbine engine together with the overall transmitted horsepower to weight ratio, an epicyclic gear train is used to transmit power from the turbine section to the propeller shaft (as in PWC PT6 engine) or to the fan shaft (as in Honeywell TFE-731 engine). In order to achieve an optimum design in view of structural integrity, the stress characteristics of each component of the epicyclic gear train needs to be optimized. In general, the external gear mesh (as in the sun and planet mesh), needs a back up rim to tooth thickness ratio of not less than 1.2. However, this is not always the case for internal gear mesh such as the ring gear. The objective of this paper is to present analytical results on the stress behavior of the ring gear under different loading conditions. Three dimensional finite element method is employed to study the internal tooth fillet stress under the effects of fillet radius, gear rim thickness, pressure angle and helix angle. This study is the first part of a work aiming to determine the failure mode of the ring gear and leading to design optimization of epicyclic systems.Copyright