Acoustical optimization of a train gearbox based on overall system simulation

The present article deals with the simulative representation and optimization of acoustic properties of a train gearbox with one helical gear stage. At first, a dynamic model of the initial gearbox based on manufacturer construction parameters was built up. Based on this model, the gear mesh excitation as a main source of structure-borne sound has been calculated. Within the simulation model all relevant influences on gear mesh excitation e.g. housing and shaft deformations or bearing stiffnesses have been considered by including flexible structures. By reference to these simulation results, the first optimization step was to change gear micro geometry to reduce system excitation. Based on analysis of system dynamics, as well as the calculation of averaged surface velocities, critical rotational speeds have been identified for a given input torque. For these critical rotational speeds, interface parameters, which are necessary for the following numerical sound radiation simulation, have been determined. On the basis of the simulated mode shapes and operational deflection shapes, a structural optimization of the gearbox housing was performed by considering space and mass specifications. The acoustic characterization of different optimization variants have been realised by comparing the emitted sound power levels determined by numerical simulation.