Theoretic and experimental structures of a composite beam filled with magnetorheological fluid

• Main Authors: Jeng, Yue-Shih, 鄭岳世
• Other Authors: Yeh,C.S.
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/59358587348341934230

博士 === 國立臺灣大學 === 應用力學研究所 === 91 === The main contribution in this dissertation is the study on the major effect of the magnetic field direction and the magnetic field strength on the constitutive law and the governing equation of the MR fluid. (MagnetoRheological Fluid). Based on the Euler and the Timoshenko beam theory respectively, two kinds of governing equations, which described the behavior of the composite beam containing MR fluid, were presented. From the comparison of the theoretical prediction and the experimental results, it was found that the Euler beam theory was not suitable to be used to describe vibration behavior of the composite beam containing MR fluid, and the Timoshenko beam theory could be used to describe the vibration behavior of the composite beam containing MR fluid very well. The main reason was that the transverse displacement was composed by transverse displacement induced by bending moment and shear force. In addition, in the practical MR fluid, the transverse displacement induced by shear force was more large than to be neglected. The composite beam containing MR fluid was supported mainly by MR fluid whenever the beam was loaded by shear force. Owing to the above reasons, the Euler beam theory, which assumed the shear strain to be neglected, could not be used to describe the vibration behavior of the composite beam containing MR fluid. However, since the shear strain effect was took into account in the Timoshenko beam theory, the parameters could be adjusted to completely describe the overall behavior of the composite containing MR fluid when the experimental results were compared with theoretical prediction. After the comparison of the theoretical prediction and the experimental results, the material constants the and the were successfully measured out. Besides, the relationship between the material constants, the magnetic field direction and the magnetic field amplitude were obtained. Since the one dimension vibration behavior of one beam could be represented by the vibration behavior of the continuous system with one degree of freedom, several material constants of the MR fluid such as the damping ratio, generalized stiffness and the generalized mass, etc, could be derived. Besides, the natural frequency and the period could also be estimated out. Except the measurement of the material constants, under the fundamental property of the MR fluid, both the frequency response when partly loaded by magnetic field and the frequency response when loaded one side by magnetic force were preliminarily obtained. In this dissertation, owing to the magnetic property of the MR fluid particle, when the MR fluid vibrated, the induced signal were preliminarily measured out. In addition, by this operation mechanism, the frequency response of the composite beam containing MR fluid in the variable magnetic field could be further studied. In conclusion, from the experimental results, an innovative MR fluid design and mechanism such as a sensor, local magnetic field design and the magnetic force loaded one side mechanism were proposed and approved. In addition, the material constants and were successfully measured out. From several experiments, it is believed that it will be highly potential in the MR fluid application.