Master of Engineering, Research
Faculty of Engineering
Zhou, Yang, MR elastomers for structural control, Master of Engineering, Research thesis, Faculty of Engineering, University of Wollongong, 2009. http://ro.uow.edu.au/theses/3144
This dissertation focuses on a basic understanding of the behaviour of Magnetorheological elastomers (MREs) and their application as MRE bearings for vibration controlling the structural systems. MREs are an important member of the group of smart materials and as such have attracted increasing interest because their modulus can be controlled by an external magnetic field.
Because MRE based devices usually work in a dynamic mode, the study of MRE properties under these conditions is essential for its practical application. The relationship between the dynamic shear stress and shear strain in various magnetic fields, including different strain amplitudes and frequencies, were measured. The stress-strain data forms elliptical curves which show that MRE behaves as if it possessed linear viscoelastic properties.
Based on these experimental results, a viscoelastic solid model with four parameters was proposed to predict the performance of MRE. In this model a spring element was placed in parallel with a 3-parameter standard viscoelastic solid model. A MATLAB optimization algorithm was used to identify the four parameters under various working conditions (magnetic field, strain amplitude and frequency). A comparison between the experimental results and the model predictions proved that the four-parameter viscoleastic model can accurately predict the performance of MRE.
A building model, three stories high, was constructed using MATLAB SIMULINK to evaluate the performance of an MRE device in structural control. Three controllers, passive on, passive off and bang-bang control strategy were used to compare the response of each storey to displacement and acceleration. In addition, the performance of an MRF damper and an MRE device in structural control, where the resultant peak force was selected as a criterion in the evaluation process, was compared and discussed. The effectiveness of an MRE bearing in structural control was well justified.
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