A coil external mount featuring carefully-tailored magnetorheological grease: Design, characterization, and modeling

To avoid performance degradation of the magnetorheological (MR) mount due to the traditional inside built-in coil structure and the settling of the MR fluid, a coil external MR mount featuring carefully-tailored MR grease considering sedimentation and zero-field viscosity balance is proposed and its dynamic performances are experimentally investigated. Firstly, a kind of composite lithium-based MR grease is firstly prepared by adjusting the content of Lithium based thickener in the lubricating grease matrix to meet the requirement of relatively low zero-field viscosity under the premise of maintaining stability, and its rheological properties under shear and squeeze mode are studied. Then the coil external MR mount operating in the radial valve-squeeze mixed mode is designed, with an evaluation of the magnetic circuit focusing on its capability to supply a satisfactory magnetic field. The dynamic behavior of coil external MR mount utilizing the carefully-tailored MR grease as the carrier fluid under various magnetic fields has been investigated using oscillatory cycles over a frequency range of 0.5–5 Hz for various displacement amplitudes from 0.5 to 1.5 mm. The results demonstrate that the novel MR grease mount could provide large damping force up to 17.81 kN with a limited stroke. Finally, a Bouc–Wen–Baber–Noori parametric model is proposed to describe the necking hysteretic behavior of the proposed MR grease mount, and a numerical study was conducted to investigate the effects of some key parameters of the model on force-displacement loops. It shows that the model agrees well with the experimental data and it can be used for the dynamics analysis and the real-time control.