Simulation of Accessory Drives Bevel Gears Dynamic Conditions

Abstract

Bevel gears of modern aviation motors operate at high rotation velocities and transmitted torques. High dynamic load in bevel mesh due to impact interaction of teeth in contact actuates gear rim oscillations. Coincidence of dynamic load frequency and bevel gear natural frequency of nodal diameter can cause oscillation amplitude grow and gear rim breakdown. By harmonic response analysis it is shown, that highest stresses in gear rim appears during gear oscillation by two or three nodal diameters. Gear root is a stress concentration in this case. In this paper methods of bevel gears dynamic behavior simulation are considered. A 3D solid dynamic model of bevel gear drive with transient contact interaction between pinion and gear by curvilinear teeth subject to tooth profile modification has been developed. An actuation was made by kinematic way by applying rotational velocity to driving pinion. A transmitted torque is applied to driven gear. An energy dissipation in gear material is considered in model. A transmission error of bevel gears depending on profile modification, transmitted torque and diaphragm stiffness is calculated. It is shown, that applying tooth profile modification helps to avoid stress concentration on teeth flank, decreases transmission error and derivatives of it’s function. As a result of calculation a function of disturbing force, actuating in gear mesh, dynamic transmission error and first principal stresses of gear crown face in time domain has been obtained. A spectral analysis of disturbing force and first principal stresses of gear rim is executed. As a result, it is shown, that gearing mesh is a source of poly-harmonic excitation of bevel gears. The maximum amplitude in contact force spectra is at frequency four times greater, than tooth frequency, and the maximum amplitude in first principal stresses of gear crown face spectra is at tooth frequency. Using a first principal stresses law of variation a new criterion of bevel gear rim strength is obtained.