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Title: Dynamic behaviour of an impact system with SMA restraint
Author: Sitnikova, Elena
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2010
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The interest in use of SMAs in vibrational systems is stimulated by their ability to dissipate energy and consequently their potential to control the dynamic behaviour of the system. In this thesis nonlinear dynamics of an impact oscillator with one sided motion constraint made of a shape memory alloy (SMA) is investigated. The pseudoelastic behaviour of SMAs is characterized by high non-linear recovery deformations and energy dissipation due to the occurrence of hysteresis. The thermo-mechanical description of the SMA element follows the formulation proposed by Bernardini et al. [1,2]. Extensive numerical investigations into the influence of the forcing parameters, which characterize the intensity of the load acting on the SMA has been carried out. They suggest that the system can exhibit complex dynamic responses, which if appropriately controlled can be used for vibration reduction. The comparison with the equivalent elastic oscillator response has shown that the use of the SMA can significantly change the dynamic response of the system. Whereas low amplitude regimes are not affected by the SMA element, at resonances when the response amplitudes are large, a significant vibration reduction is achieved due to the phase transformation hysteresis loop. Two types of periodic response co-existence is also revealed in these regions. At the same time, in other frequency ranges the existence of additional modes of motion in the pseudoelastic oscillator can cause new large amplitude responses (both periodic and chaotic) to be generated, as well as eliminate some of the co-existing responses. Various bifurcation scenarios are constructed and the influence of the SMA element is discussed. To verify the obtained theoretical predictions, an experimental rig was designed and limited experimental studies have been conducted. The substantial response amplitude reduction at resonances has been captured, as well as the jumps to higher amplitude responses due to the softening behaviour of SMA. The numerical results appeared to be in a good agreement with the experimental data.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available