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Title: Mechanical and microstructural behaviour of tangled metal wire devices
Author: Chandrasekhar, Kartik
ISNI:       0000 0004 6350 3617
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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As the push towards the use of lighter and more efficient materials continues, energy dissipation from vibrating structures made from such materials is growing in importance. Viscoelastic materials have most often been employed to tackle vibration problems. In several applications, such as in the space and defence fields, the operating conditions usually do not allow for such solutions to be utilised. Tangled metal wire (TMW) devices offer an alternative damping strategy. Since the microstructure of such devices is made of metallic materials, they operate resiliently over a wide range of environments. The microstructure of a typical TMW device is made of metal wires that have been woven and compressed into an entangled state. Although they possess favourable properties, the manufacturing process makes the microstructure very complex, and the mechanical behaviour, as a result, tends to be unpredictable. The main theme of this thesis links the mechanical behaviour of TMW devices to their microstructural characteristics. A new algorithm is developed to study the microstructure of TMW devices from images obtained via microcomputed tomography (μ-CT) scanning. Following the application of compressive loads during the μ-CT scanning, it has been shown, for the first time, how the complex microstructural state evolves under different loading conditions. Parallel to this, displacement controlled experiments are performed on the TMW devices under quasi-static, low frequency, and high frequency loading conditions in an effort to ascertain the important phenomenological effects that dominate their response. Various analytical models are also explored and analysed with the aim of identifying an appropriate model for TMW devices. An analytical model, the frictional Zener model, is developed further to replicate the experimentally observed force-displacement hysteretic trends. The developed models, named the multi-chain frictional Zener models, include various additional terms to the basic model. Parameters are identified for the proposed models, and a model that gives acceptable accuracy with respect to experimentally observed hysteresis is found. This model is able to exhibit the spring-like nature of TMW devices, and it provides energy dissipation via classical Coulomb friction. The terms in the model are justified through analysis of the image processing results. Previous researchers have thus far not been able to fully justify the reasons why TMW devices behave the way they do since the microstructure has not been completely understood. The benefit of studying both the microstructural and mechanical properties of TMW devices in the manner outlined above is that a more holistic reasoning for observed behaviour is attained. The relatively simple proposed analytical model can be used to predict dynamic response when TMW devices are applied to real structures. As the confidence levels in the understanding of the TMW device microstructure and modelling aspects increase, more applications can take advantage of the favourable mechanical properties (especially in terms of energy dissipation) TMW devices showcase.
Supervisor: Rongong, J. A. ; Cross, E. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available