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A novel concept of a compact magnetorheological valve is proposed based on the advance characteristics of magnetorheological fluid. The structural design consists of a meandering pattern formed by multiple annular and radial gaps in order to extend the flow path length of magnetorheological fluid. Extending the flow path of magnetorheological fluid is important in order to increase the density of effective area, so that the rheological properties of magnetorheological fluid can be widely regulated in a small size magnetorheological valve. The main objective of this article is to show that the pressure drop as one of the key performance indicators in a magnetorheological valve can be significantly increased using multiple annular and radial gaps configuration. In order to demonstrate the magnetorheological valve performance, simulation work using magnetic simulation software called finite element method–based software for magnetic simulation is conducted and combined with the pressure drop calculation using the derived magnetorheological valve model. Simulation results show that the magnetorheological valve with multiple annular and radial gaps is able to improve the achievable pressure drop. The discussion on the effect of gap size variations on the achievable pressure drop and the operational range of magnetorheological valve is also presented.

In this study, a new magnetorheological (MR) grease was made featuring plate-like carbonyl iron (CI) particles, and its magnetic field-dependent rheological properties were experimentally characterized. The plate-like CI particles were prepared through high-energy ball milling of spherical CI particles. Then, three different ratios of the CI particles in the MR grease, varying from 30 to 70 wt% were mixed by dispersing the plate-like CI particles into the grease medium with a mechanical stirrer. The magnetic field-dependent rheological properties of the plate-like CI particle-based MR grease were then investigated using a rheometer by changing the magnetic field intensity from 0 to 0.7 T at room temperature. The measurement was undertaken at two different modes, namely, a continuous shear mode and oscillation mode. It was shown that both the apparent viscosity and storage modulus of the MR grease were heavily dependent on the magnetic field intensity as well as the CI particle fraction. In addition, the differences in the yield stress and the MR effect between the proposed MR grease featuring the plate-like CI particles and the existing MR grease with the spherical CI particles were investigated and discussed in detail.

This paper presents mitigation behaviour of magnetorheological (MR) damper operated with a mixed working modes. A combination of the shear and squeeze modes is employed in the structure of MR damper to obtain the field-dependent normal yield stress as well as strengthen the squeeze effect. The experimental evaluation shows that when the piston is squeezing the bottom gap from the stroke of 25 to 26 mm, the sudden increase of squeeze force is observed confirming the existence of the mitigation effect. It is also observed that the magnitude of mitigation force is positively correlated with the magnitude of current given to the electromagnet. The measured peak mitigation forces are ranged from 722 N to 1032 N when the electromagnet currents are varied from 0.2 A to 0.8 A, respectively. The variable mitigation effect indicates that the concept can be further discussed as a potential impact protection feature in an MR damper.

This paper presents a simulation study of electromagnetic circuit design for a mixed mode Magnetorheological (MR) damper. The magnetic field generated by electromagnetic circuit of the MR damper was simulated using Finite Element Method Magnetics (FEMM) software package. All aspects of geometry parameters were considered and adjusted efficiently in order to obtain the best MR damper performance. Eventually, six different parameters approach were proposed; the selection of materials, the polarity of coils, the diameter of piston, piston rod and core, the shear and squeeze gaps clearance, the piston pole length and the thickness of housing.