TJ644 : An experimental investigation on magnetorheological fluids stability baxsed on Surfactants
Thesis > Central Library of Shahrood University > Mechanical Engineering > MSc > 2019
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Abstarct: MR fluids are a kind of suspension and a category of intelligent materials that in the presence of external actuator, their rheological properties such as viscosity and yield stress change very quickly and less than a millisecond. The most important feature of these fluids is the phase change from liquid to semi-solid state, which their yield stress can be quickly controlled by the appliyng of magnetic fields. There are basically three components to the composition of a MR fluid including the magnetic particles, the carrier fluid, and the stabilizing additives. The deposition of suspended particles in MR fluids is due to the difference in particle density and carrier fluid. In systems such as earthquake dampers where the system is rarely activated, because it is difficult to disperse these particles, their sedimentation should be avoided as much as possible. Many methods have been proposed to improve the stability of MR fluid that most of these methods increase the viscosity of the state without applying a magnetic field. In this study, we investigated the effect of wormlike micelles formation on carrier fluid to improve MR fluid stability. Micelles are a group of dense surfactants that are dispersed in a liquid colloid. In many micellar solutions containing hydrocarbon baxse fluid, lecithin is used as a surfactant. To compare MR fluid with baxse solution containing creamy micelles the other two concentrations are made of micellar solution, one is made above the concentration of worm-like micelles and the other is made below. After preparing the baxse solution for making MR fluid, iron powder with 65% by weight was added to the solution. The target MR viscosity value is 254 Pa.s without applying a magnetic field which is well within the range of other studies. One of the common models that can predict the rheological behavior of MR fluid is the Herschel-Bockley model. According to this model, the yield stress at the magnetic field of H = 91 (kA / m) for the MR fluid is 4319.76 Pascal. MR fluid samples were measured for one month to compare their stability. The amount of MR-W fluid deposition, which is the target fluid, is approximately equal to the MR-H fluid containing the highest concentration of baxse solution. This behavior reflects the effect of the worm-like micelles network, which improves the stability of the particles. The settling rates of MR-W and MR-H fluids were 18.2 and 17.8% after one month, respectively. Special Features of MR Fluid In this study, it is easy to disperse the carrier fluid after a long time.
Keywords:
#Magnetorheological fluid stability #Worm-like micelles #Maxwell model #Yield stress #Lecithin Link
Keeping place: Central Library of Shahrood University
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Keeping place: Central Library of Shahrood University
Visitor: