Novel Design of Torsional Hollow Shafts with Acoustic Black Hole Profile for Vibration Attenuation

Abstract

The torsional vibration phenomenon is a common issue in various transmission systems, such as vehicles, machinery, marine, aviation and aerospace. The serious torsional resonance may generate the additional cyclic stress in the transmission system in operation, subsequently leading to damage or failure. In this paper, a novel torsional hollow stepped shaft design method is proposed to effectively attenuate the torsional vibration amplitude, inspired by the bending beam with the acoustic black hole (ABH) profile. By comparing dynamic equations of the bending beam to the torsional shaft with the ABH profile, it can be concluded that both dynamic equations exhibit similarities. Three types of torsional shafts with the ABH profile are designed and fabricated by additive manufacturing. Transient torsional experiments are conducted with a high-torque torsional experimental apparatus, and amplitude attenuation characteristics are investigated by finite element method (FEM), with solutions compared against experimental results. The comparison between the shaft with epoxy resin and the pure aluminum alloy shaft further confirms that the power law cross section with an ABH profile is the primary mechanism for vibration attenuation, while the epoxy resin merely plays a supplementary role. Accordingly, three engineering torsional shafts with the ABH profile are designed and subjected to numerical solutions. Results indicate that torsional natural frequencies of all three novel shafts are significantly reduced compared to conventional shafts. Moreover, whether subjected to the periodic impact load or the irregular transient load, all three novel shafts present significant vibration attenuation advantages, which can be flexibly selected under the different operating conditions.