Multifaceted Vibration Absorption of a Rotating Magnetic Nonlinear Energy Sink --- Part I: Numerical and Theoretical Studymultifaceted Vibration Absorption of a Rotating Magnetic Nonlinear Energy Sink --- Part Ii: Experimental Validation

Abstract

Hazardous failures of engineering structures can be prevented by implementing passive vibration absorbers. Although tuned mass dampers (TMD) are used most frequently in practice, nonlinear energy sinks (NES) offer a broader frequency performance due to their targeted energy transfer (TET) mechanisms. However, this behavior occurs only in a limited amplitude range. In this two-part series, the vibration suppression of novel monostable and bistable magnetic rotary nonlinear energy sinks (MRNESs) are studied over a range of excitation magnitudes for impulse and harmonic excitation. In this part, the MRNESs are tuned to achieve hybrid TMD and NES-like behavior. The medley of in-well, cross-well, and rotational TET mechanisms responsible for their performance are related to their underlying Hamiltonian systems and lower boundaries of chaos. For impulse excitation, rotational, subharmonic, and nonlinear beat responses lead to efficient energy dissipation. For harmonic excitation, the MRNEs' frequency responses can resemble a TMDs' or exhibit chaotic-like cross-well and rotational strongly modulated responses. Consequently, MRNESs can overcome the shortcomings of many NESs, which are inefficient at low excitation magnitudes, while also outperforming linear TMDs when the systems' parameters are detuned at large excitation magnitudes, for both impulse and harmonic excitation.Nonlinear energy sinks (NES) are passive vibration absorbers that have gained popularity because of their broad-frequency targeted energy transfer (TET) mechanisms. Despite their advantages over classic linear tuned mass dampers (TMDs), the use of NESs in practical engineering settings is limited because of their amplitude-dependent efficiencies. In this work, the vibration suppression of a monostable and bistable magnetic rotary nonlinear energy sink (MRNES) was studied experimentally to verify its ability to act as an efficient passive vibration absorber. A cantilever beam was used as a primary system and an MRNES was attached to the free end of the beam. The beam was subjected to impulse excitation, using an impact, and harmonic excitation, using a shaker. The MRNES's succession of rotational, subharmonic, and nonlinear beat responses, for impulse excitation, and TMD and NES-like frequency responses, for harmonic excitation, qualitatively matches the numerical results from the companion paper. For all excitation magnitudes considered, the MRNES reduced the primary system's settling time and resonant peak by 68 to 82% and 67 to 95%, respectively, therefore confirming its ability to perform efficiently over a broad range of excitation magnitudes due to its TMD characteristics and various TET mechanisms. Furthermore, the MRNES may be more viable for practical use than other hybrid NESs since it is compact, highly customizable, and does not rely on impacts or complicated spring arrangements for its non-linearity.

Keywords: Non-contact magnetic force enhances a rotary NES's vibration suppression.MRNES overcomes drawbacks of many NESs while outperforming TMDs when detuned.MRNES utilizes TMD and NES-like behaviors at different excitation magnitudes.MRNES's chaotic-like cr