Efficient evaluation of the acoustical behavior of gearboxes with various gear blanks using frequency based substructuring

In several industrial branches, the acoustical behavior of gearboxes plays a major role. In most cases, the transmission's noise is perceived as an annoying sound, the so-called gear whine with narrow-band spectral components. This tonal noise is caused by the gear mesh and is mainly dependent on the number of teeth as well as the corresponding rotational speed. In combination with the frequency-dependent structure-borne and airborne sound transfer paths of the gearbox and its subsequent systems, different speeds may lead to resonant system response due to the variable excitation frequencies. The purpose within the design process of gearboxes is the identification of such critical acoustic load conditions and the deviation of adequate measures to improve the acoustical behavior. As well known from other applications, the frequency based substructuring provides a methodology to evaluate the vibrations of a system consisting of different subsystems represented by frequenc y-dependent admittance functions. A main advantage of this method is that the single subsystems are independent from the mounting conditions. Within the present paper, the frequency based substructuring approach is used to evaluate the dynamic behavior of a single-stage gearbox with different gear blanks but equal tooth geometries. After a short introduction of the corresponding theory, the application of the frequency based substructuring method on gearbox dynamics is shown. In a next step, the simulation results are compared to experimental data obtained by test bench measurements with two different types of blanks - a reference model with no modifications as well as a gear with a metal foam core to change the stiffness of the gear blank significantly. Finally, the influences of different gear blanks are shown and discussed based on simulation results.