This work describes the magnetic analysis of an innovative double cup-shaped gap magnetorheological (MR) clutch featuring with three smart MR gels. Four kinds of Halbach array is used to excite the MR gel. The apparatus is designed by using a magneto/mechanical finite element method model, which is numerical calculated by COMSOL Multiphysics software. After describing the configuration, the transmittable torque in the designed MR clutch is derived based on the Bingham-Plastic field-dependent constitutive model of the MR gel. Considering the viscosity in the model building, such as the shear yield stress, which also various with change of magnetic flux density. The magnetic flux density distribution, the shear yield stress distribution, the dynamic viscosity distribution and the shear stress distribution inside the MR gel are obtained and carefully studied. Furthermore, the chain layer of internal cylindrical part, external cylindrical part, internal disc part and external disc part with lowest shear stress are found to calculate the transmission torque and slip torque. Then, the structure of the prototype is optimized based on multi-physics analysis. Finally, the optimal MR clutch is developed and the magneto-static torque is tested with detail analysis.

This paper investigates the impact of temperature on the rheological properties of magnetorheological (MR) grease containing carbonyl iron suspended in lithium-based grease Lithium-based MR grease with 70% weight fraction of carbonyl iron is firstly prepared by mechanical mixing. The apparent viscosity and shear stress as a function of shear rate under different temperatures and magnetic field strengths are measured and discussed. It is found that the influence of temperature on apparent viscosity reduces with the increase of magnetic field strength. The dynamic properties of MR grease are obtained under oscillatory shear test. The influences of strain amplitude, driving frequency and magnetic field on the dynamic properties of MR grease at different temperature are discussed. The results demonstrate that the enhancement of temperature leads to the increase of storage modulus and the reduction of the loss factor. Microstructural variation of grease matrix at different temperature is proposed as an explanation of the rheological changes of MR grease.

This paper studies the dynamic rheological behaviors of magnetorheological (MR) gels containing different CIP weight fractions suspended in polyurethane (PU).

With the development of intelligent communications and stealth technology in the military field, electromagnetic wave pollution cannot be ignored, and absorbing materials have entered people’s field of vision and gradually become a research hotspot. The ideal absorbing material should have the characteristics of “strong, wide, thin, and light”, but a single absorbing material often cannot meet the above conditions. At present, absorbing metal powder combined with two-dimensional carbon nanomaterials (such as carbon nanotubes, graphene, etc.) has became a trend. This article focus on a three-layer composite of Fe₃O₄, Carbon nanotubes@ Fe₃O₄, Carbon nanotubes@Graphene nano-platelets@ Fe₃O₄, which was synthesized by solvothermal method. The results show that the electromagnetic wave absorption performance of the three-layer foam at a thickness of 3.0 mm is more excellent. The minimum of RL can reach −67.0 dB, and the effective bandwidth is above 5.0 GHz. All this is due to the synergy of dielectric and magnetic loss between Fe₃O₄, CNTs, and GN, the increase of interface polarization and the path of electromagnetic wave reflection and scattering by three-layer foam.

In order to investigate the multiphysics in the recoil process of magnetorheological damper, independent three-stage magnetorheological damper of double rod has been designed. The magnetorheological gel with carbonyl iron powder mass fraction of 70% (MRG-70) has been prepared and the steady-state shear test was carried out for obtaining the consistency coefficient k and the non-Newtonian index n of the Herschel–Bulkley model. MRG-70 has been applied to the damper and the motion analysis of the recoil part has been carried out by combining the law of chancing of the bore resultant force of a certain type of fixed artillery. Results of the theoretical analysis and numerical calculation of multiple physical fields for damper showed: (1) there was a scattered magnetic flux inside the damper. The magnetic field was generated by the combined coil with a high degree of nonlinearity and time variability; (2) the internal energy dissipation of damper comprises five parts, in which Poiseuille pressure flow loss and Couette viscous flow loss were the primary and controllable part of the damper. The temperature of each pole reaches a peak value, and it is different at different times; the pressure drop at the magnetic pole was less than the pressure drop at the coil; (3) the dynamic viscosity of the central axial surface of the effective damping channel shows obvious nonlinearity and time variability from the spatial and time dimension, and varies very sharply at each pole, and the peak value fluctuates with the position.