Attenuation of torsional vibrations in a periodic shaft with gears 2022-36-0005
Mechanical transmissions with gears and shafts transmit torque and speed. However, besides transmitting power, the assembly can behave as torsional vibration amplifier for certain frequencies, and the geometry has a major importance in this context. Using the concept of periodic structures, it is possible to obtain frequency bands with high attenuation, called band gaps. In these wide frequency ranges of attenuation, the structure acts as a mechanical filter, avoiding elastic wave propagation and, therefore, vibration modes. The object of this investigation is the computational modeling of torsional vibrations using the spectral element method and the experimental testing of a periodic shaft with gears, designed to filter both the gear mesh frequency and the engine-related frequency. Hence, a real gearbox shaft is modified to have 3-unit cells and to generate the attenuation frequency bands desired for this application. The effect of gear assembly on the periodic shaft behavior due to interference fit is discussed in the computational model updating. It is shown that a shaft with periodically assembled gears produces a wide band gap and that the coupling of such a shaft with other inertias can generate defect modes within the band gaps, which can compromise the vibration attenuation. Numerical and experimental results are analyzed considering the free-free boundary condition.