共查询到19条相似文献,搜索用时 206 毫秒
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提出了一种磁流变液构成的类梯度结构,并通过理论建模、数值计算和实验研究了该结构的振动传递特性.磁流变液在磁场作用下具有液固转换的特殊理化性质,而液固转换过程就是磁流变液的振动传递阻抗变化过程.因此,基于磁流变液的这一特性,通过控制磁场,构建了类梯度结构.基于弹性波传递的一维波动方程,建立了垂直入射的弹性波在类梯度结构中传递的波动方程.然后,使用连续介质的离散化方法和传递矩阵法进行求解,得到振级落差的表达式,对其进行数值计算,分析类梯度结构的振级落差随弹性波频率和磁场强度的变化趋势.最后,对类梯度结构的振动传递特性进行了实验研究,分析了磁场强度对类梯度结构振动传递特性的影响.研究结果表明,与均匀场作用的磁流变液相比,类梯度结构对弹性波的衰减效果更好,且该结构具备良好的可调控特性. 相似文献
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旋转磁场作用下磁流变液颗粒运动及结构演化的模拟 总被引:9,自引:1,他引:8
通过对旋转磁场作用下磁流变液一定数目颗粒运动的数值模拟,在旋转平面内得到盘状聚集结构,在垂直于旋转平面的平面内得到层状结构,得出旋转磁场作用下磁流变液的结构特点。在模拟过程中颗粒受到磁场作用力简化为磁偶极子间相互作用。 相似文献
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磁流变智能液场致微结构变化的Monte Carlo模拟 总被引:5,自引:1,他引:4
从磁流变液中存在的各种相互作用势出发,对N=100个球形羰基铁颗粒均匀分布于一正方形二维体系之中的物理模型,利用MonteCarlo方法和Metroplis算法着重计算了磁流变智能液的场致微结构变化。计算结果表明,磁流变液(MRF)的流变效应在外磁场中的变化是由于其MRF中磁性颗粒的成链团簇有序化所致。这与磁流变液在外磁场中熵的下降和对MRF的光学显微镜观察结果是一致的。 相似文献
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Experimental study and CFD simulation of rotational eccentric cylinder in a magnetorheological fluid
In this study, a magnetorheological (MR) fluid is prepared using carbonyl iron filings and low viscosity lubricating oil. The effects of magnetic field and weight percentage of particles on the viscosity of the MR fluid have been measured using a rotational viscometer. The yield stress under an applied magnetic field was also obtained experimentally. In the absence of an applied magnetic field, the MR fluid behaves as a Newtonian fluid. When the magnetic field is applied, the MR fluid behaves like Bingham plastics with a magnetic field dependent yield stress. Afterward, the results compared with those of CFD simulation of two eccentric cylinders in the MR fluid. Results show that the influences of MR effects, caused by the applied magnetic field, on the model characteristics are significant and not negligible. The viscosity is enhanced by increasing of the magnetic field, eccentricity ratio and weight percentage of suspensions. The MR effects and increasing of weight percentage and eccentricity ratio also provide an enhancement in the yield stresses and required total torque for rotation of inner cylinder. Also the simulation results indicate a good representation of the experiment by the model. 相似文献
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Rajesh Patel 《Journal of magnetism and magnetic materials》2011,323(10):1360-1363
Mechanism of structure formation in bidispersed colloids is important for its physical and optical properties. It is microscopically observed that the mechanism of chain formation in magnetic nanofluid based magnetorheological (MR) fluid is quite different from that in the conventional MR fluid. Under the application of magnetic field the magnetic nanoparticles are filled inside the structural microcavities formed due to the association of large magnetic particles, and some of the magnetic nanoparticles are attached at the end of the chains formed by the large particles. The dipolar energy of the large particles in a magnetic nanofluid matrix becomes effective magnetic permeability (μeff) times smaller than that of the neutral medium. Inclusion of magnetic nanoparticles (∼10 nm) with large magnetic particles (∼3-5 μm) restricts the aggregation of large particles, which causes the field induced phase separation in MR fluids. Hence, nanofluid based MR fluids are more stable than conventional MR fluids, which subsequently increase their application potentiality. 相似文献
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M.A. BramantyaT. Sawada 《Journal of magnetism and magnetic materials》2011,323(10):1330-1333
Structure of magnetorheological (MR) fluids depends on the strength of the magnetic field applied and on the mode of its application. The ultrasonic wave propagation velocity changes under the effect of an external magnetic field as a result of formation of clusters arranged along the direction of the field in the MR fluids. Therefore, we propose a qualitative analysis of these clustering structures by measuring properties of ultrasonic propagation. Since the MR fluids are opaque, the non-contact inspection using this ultrasonic technique can be very useful. In this study, we measured ultrasonic propagation velocity in MR fluid influenced by an external magnetic field for different swept rate precisely. With increasing magnetic field intensity, the changes of the ultrasonic wave velocity are more pronounced. Sedimentation effect takes place in certain time for different swept rate due to magnetic particle size and it follows linear relationship in log scale. Significant differences of the ultrasonic wave velocity are established between the case when the field is swept at a constant rate and the case when it is stepped up. 相似文献
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Wanquan Jiang Yanli ZhangShouhu Xuan Chaoyang GuoXinglong Gong 《Journal of magnetism and magnetic materials》2011,323(24):3246-3250
A type of dimorphic magnetorheological (MR) fluid was prepared by adding wire-like iron nanostructures into the conventional carbonyl iron based MR fluid. The Fe nanowires were synthesized through reducing Fe2+ ion with excessive sodium borohydride in aqueous solution. The rheological behaviors of the dimorphic MR fluids were measured with a rotational rheometer and the sedimentation properties were also studied in this work. It was found that the Fe wires additives can greatly enhance the stress strength of the dimorphic MR fluids comparing with the conventional MR fluids. The sedimentation of the dimorphic MR fluids was also mitigated greatly. 相似文献
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Semi-active vibration control based on magnetorheological (MR) materials offers excellent potential for high bandwidth control through rapid variations in the rheological properties of the fluid under varying magnetic field. Such fluids may be conveniently applied to partial or more critical components of a large structure to realize more efficient and compact vibration control mechanism with variable damping. This study investigates the properties and vibration responses of a partially treated multi-layer MR fluid beam. The governing equations of a partially treated multi-layered MR beam are formulated using finite element method and Ritz formulation. The validity of the proposed finite element formulations is demonstrated by comparing the results with those obtained from the Ritz formulation and the experimental measurements. The properties of different configurations of a partially treated MR-fluid beam are evaluated to investigate the influences of the location and length of the MR-fluid for different boundary conditions. The properties in terms of natural frequencies and loss factors corresponding to various modes are evaluated under different magnetic field intensities and compared with those of the fully treated beams. The effect of location of the fluid treatment on deflection mode shapes is also investigated. The forced vibration responses of the various configurations of partially treated MR sandwich beam are also evaluated under harmonic force excitations. The results suggest that the natural frequencies and transverse displacement response of the partially treated MR beams are strongly influenced not only by the intensity of the applied magnetic field, but also by the location and the length of the fluid pocket. The application of partial treatment could also alter the deflection pattern of the beam, particularly the location of the peak deflection. 相似文献
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Kyung-In JangByung-Kwon Min Jongwon Seok 《Journal of magnetism and magnetic materials》2011,323(10):1324-1329
A model that considers the mutual interaction between particles and the external field in a magnetorheological (MR) fluid is proposed. The model predicts the magnetization, interaction energy density, and shear stress against an imposed strain along the planar direction under a uniform magnetic field. Using the Lekner summation method, slowly convergent magnetization functions are transformed into rapidly convergent ones. By applying the proposed model to an application suitable for commercial clutches and dampers working in direct shear mode, it is revealed that the mean magnetization vector and the associated functional quantities of the MR fluid behave harmonically with respect to the imposed shear strain. 相似文献
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Kyung-In Jang Byung-Kwon Min Sang Jo Lee 《Journal of magnetism and magnetic materials》2009,321(9):1167-1176
Magnetorheological (MR) fluid is used for various applications due to its controllable viscosity. To predict the behavior of MR fluid under certain three-dimensional (3D) magnetic and shear strain fields, it is essential to model the fluid in an appropriate manner. The behavioral models used in the previous research, however, have serious limitations because most of them oversimplify the inter-particle interactions and employ assumptions valid only under specific geometric configurations and field conditions. In this study, a new model that can predict the behavior of MR fluid under arbitrary 3D magnetic and shear strain fields is proposed. The present work considers an MR fluid configured as a 3D infinite lattice structure. Using the proposed model, the shear stress components themselves, not the dipolar interaction energy, are calculated directly to avoid the mathematical singularity otherwise encountered. The resulting stress functions of the proposed model are transformed into rapidly convergent functions using the Lekner summation method. Finally, the characteristics of the stiffened MR fluid under a magnetic field are investigated using the transformed functions. Numerical computations on the original and transformed functions are performed and compared under selected conditions to ensure the validity and prove the high convergence efficiency of the proposed model. 相似文献
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Gjergj Dodbiba Hyun Seo ParkKatsunori Okaya Toyohisa Fujita 《Journal of magnetism and magnetic materials》2008
In this work, properties of a magnetorheological (MR) fluid, prepared by dispersing a mixture of two types of carbonyl iron powders (CIPs) of different sizes, in an ionic liquid (N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate) that is stable from 9 °C to ca. 300 °C, have been investigated. At first, the random packing density of the mixture was computed as function of mixing ratio of CIP, in order to find out the tendency of the variation. Next, several mixtures, all having the same weight, were prepared at various mixing ratios and dispersed in the ionic liquid, in order to experimentally find the most suitable mixing ratio of CIP. Then, the magnetic clusters of the synthesized MR fluids were observed by using a digital microscope equipped with two permanent magnets, whereas the MR properties were investigated by using a rotation viscometer equipped with a solenoid coil. The experimental results pointed out that the MR fluid with 60 wt% fraction of large particles exhibited the highest MR response. 相似文献