Supplementary Information Files for 'Design and validation of a nonlinear vibration absorber to attenuate torsional oscillations of propulsion systems'

Recent developments in propulsion systems to improve energy efficiency and reduce hazardous emissions often lead to severe torsional oscillations and aggravated noise. Vibration absorbers are typically employed to palliate the untoward effects of powertrain oscillations, with nonetheless an adverse impact on cost and constrained efficacy over a limited frequency range. Recently, the authors proposed the use of nonlinear vibration absorbers to achieve more broadband drivetrain vibration attenuation with low complexity and cost. These lightweight attachments follow the concept of targeted energy transfer, whereby vibration energy is taken off from a primary system without tuning requirements. In this paper, the design and experimental investigation of a prototype absorber is presented. The absorber is installed on a drivetrain experimental rig driven by an electric motor through a universal joint connection placed at an angle, thus inducing second order torsional oscillations. Vibration time histories with and without the absorber acting are recorded and compared. Frequency-energy plots are superimposed to the system nonlinear normal modes to verify the previously developed design methodology, whereas the achieved vibration reduction is quantified by comparing the acceleration amplitudes of the primary system and monitoring the distribution of energy damped in the primary system and the absorber. The absorber prototype was found to lead to significant vibration reduction away from resonance and near resonance with the additional feature of activation over a relatively broad frequency range.