An accurate technique for pre-yield characterization of MR fluids

Abstract

This study is concerned with the characterization of two types of magnetorheological (MR) fluids (MR 122EG and MR 132DG) in the pre-yield region. A phenomenological model is proposed for characterizing the complex shear modulus of the MR fluids as a function of both the magnetic flux density and the excitation frequency using the experimental data acquired for both the fluids. The experiments were conducted with a sandwich beam structure with an aluminum face layer and MR fluid as the core layer. A nearly uniform magnetic field was applied across the sandwich beam using two ceramic permanent magnet bars. The frequency response characteristics of the sandwich cantilevered beam were subsequently measured under harmonic excitations swept in the 0 to 500 Hz frequency range considering different densities of the applied magnetic flux, ranging from 0 to 90 mT. Dynamic responses of the structure were also obtained through analysis of a finite element (FE) model developed using the classical plate theory. The frequency and field-dependent complex shear moduli of the two MR fluids were identified from both the experimental data and the FE model results. The validity of the proposed methodology is demonstrated by comparing the FE model results with the experimental data for a copper sandwich structure comprising the two MR fluids.

Soft Robotic Grippers

“…The response time of ER/MR fluids is relatively short, less than 10 ms . Their relative stiffness change ranges from a few times to a few tens of times, and generally MR fluids have shown greater changes than ER fluids . ER fluids have generally lower energy consumption power requirements, because the generation of electric fields relies only on applying an electrical potential (with no steady state current flow), while magnetic fields are proportional to electric current.…”

Dynamic characteristics and control of magnetorheological/electrorheological sandwich structures: A state-of-the-art review

“…MR/ER sandwich plate, as depicted in Figure 12, comprises base layer, sealant spacer, constraining layer, and MR/ ER fluid as the core layer. The assumptions employed in the analysis of adaptive sandwich beams (no slippage between the layers, uniform transverse displacement through the thickness, and negligible normal stress and transverse shear strain in the core and face layers, respectively) are also applicable for the analysis of the MR/ER plate structures (Choi et al, 1999;Hasheminejad and Maleki, 2009;Lu and Meng, 2006; (Eshaghi et al, 2015a). Narayana and Ganesan, 2007).…”

“…Application of FE method has been extensively reported to derive governing equations of motion of MR/ER sandwich plates under different geometry boundary conditions (Cho et al, 2005;Lu and Meng, 2006;Yeh, 2007bYeh, , 2010bYeh, , 2011aYeh et al, 2009). Eshaghi et al (2015aEshaghi et al ( , 2015c) employed a sandwich plate element, as depicted in Figure 13, to derive governing equations of motion of an MR sandwich plate. The element consisted of four nodes with 10 DOF (longitudinal displacements, transverse displacement, and slopes about x-and y-axis for the top and bottom layers), per node.…”

“…Accordingly, inappropriate application of magnetic/electric field may degrade vibration control Figure 13. Two-dimensional sandwich plate element (Eshaghi et al, 2015a).…”

The normal stress of an electrorheological fluid in compression mode

“…During this process, the ER uids transit from a liquid state to a solid-like state and the apparent viscosity increases dramatically. Because of the unique ER effect, the ER uids have broad potential in technological and industrial applications, such as sandwich structure, 6,7 damper, 8 actuator, 9 and so on. Most applications of ER materials are operated in shear mode, in which the loading direction is perpendicular to the applied electric eld.…”