NVH and design optimization of a rear electronic differential for high performance vehicle

The thesis project is the description of the optimization process with the aim of improving the vibrational performance of a rear axle differential of a high performance vehicle whose main cause of emission is the bevel gear set. The same group is fitted to different car models but only in a couple of these are heard a whistle during a certain working condition. This condition required an optimization of the differential design from the NVH point of view. Therefore it is wanted to investigate in depth what are the parameters that influence this behavior, starting from the analysis of the macro and micro geometry and continuing with the analysis of other components such as bearings, shafts and housing. The thesis is structured with an initial part about the company where the project is born and the following chapters about the fundamental concepts of bevel gear design, damage under load, introduction to sound and noise, passage from time domain and frequency domain of a real signal through the Fourier transform, measurement equipment and NVH. These concepts help the understanding of the final graphs that are the main outputs of the optimization of the differential group, therefore frequency spectrum, order analysis and order cut. Most of the focus is dedicated to the order of the bevel gear set, how it is computed and how its emission change from initial phase to post optimization process.