Numerical investigation on traveling wave vibration of bevel gears

Aircraft transmissions have the peculiar characteristics of light structures and high operating speeds, therefore relatively low flexural natural frequencies and high excitation frequencies due to rotation and meshing. Thus some dynamic phenomena, such as traveling wave vibration (T W), can be more easily encountered. However few papers can be found in the literature on TWV of gears while on the contrary it might be a problem especially for gears having thin rim and disk. This paper deals with the simulation of the disk TWV of bevel gears. 3D FEM is used to obtain the natural modes and frequencies of the gear. The response of a simplified non-rotating model of two meshing gears was entirely simulated in an Ansys environment. The numerical tests were performed considering a variable torque applied to one of the gears, the other being constrained, accounting for the meshing excitation. To simulate the rotating contact condition with respect to the gear reference systems, the dof of the nodes in contact of the two gears were coupled. Preliminary tests were performed considering one of the two gears rigid. The simulation of the TWV of gears makes it possible to identify the most critical conditions for stress and fatigue in the gear disks and therefore estimate the gear structural reliability.