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Title: The performance of a nonlinear dynamic vibration absorber
Author: Hsu, Yungsheng
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2013
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This project investigated the physical behaviour and the effectiveness of a nonlinear dynamic vibration absorber (NDVA), which was designed to possess hardening stiffness characteristics. Two types of external force excitation were considered (harmonic and random input) applied to a primary system, with attached NDVA, and the response compared. For harmonic excitation, the governing equations of motion for the entire vibrating system and the expressions for the solution were derived using the Harmonic Balance Method (HBM). Mathematical expressions for the frequency response curves of the structural system were subsequently determined. The bifurcation and stability characteristics of the identified periodic steady state solutions were obtained. The effect of the NDVA parameters (e.g., nonlinear stiffness, damping ratio, mass ratio and frequency ratio) on the vibration reduction were studied. From the numerical results it was observed that the NDVA had a much wider effective vibration reduction bandwidth compared to a linear absorber. The frequency response curve of the NDVA had the effect of moving the second resonance peak to a higher frequency away from the tuned frequency, so that the device is robust to mistuning. For random excitation, time and frequency domain techniques were used and the effect of the nonlinear absorber parameters on the vibration reduction have been determined. The experimental validation, for the nonlinear absorber considered, involved a nonlinear hardening spring supporting a mass which was designed and attached to a cantilever beam excited by a shaker. The absorber nonlinearity that occurred was due to large geometric displacement and in-plane effects. The cantilever beam, at low frequencies, acted as a linear single degree-of-freedom system. The nonlinear absorber was designed to behave as a hardening Duffing oscillator. Validation is presented for both harmonic and random excitation, supporting the previously produced analytical and numerical results.
Supervisor: Ferguson, Neil Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics