Magnetorheological fluid technology has gained significant development during the past decades. The application of magnetorheological fluids has grown rapidly in civil engineering, safety engineering, transportation, and life science with the development of magnetorheological fluid–based devices, especially magnetorheological fluid dampers. The magnetorheological fluid dampers could offer an outstanding capability in semiactive vibration control due to excellent dynamical features such as fast response, environmentally robust characteristics, large force capacity, low power consumption, and simple interfaces between electronic input and mechanical output. To address the fast growing demand on magnetorheological fluid damping technology in extensive engineering practices, the state-of-the-art development is presented in this article, which provides a comprehensive review on the structure design and its analysis of magnetorheological fluid dampers (or systems). This can be regarded as a useful complement to...

Magnetorheological fluid dampers: A review on structure design and analysis

Magnetorheological (MR) fluids typically are suspensions of spherical micron-sized ferromagnetic particles suspended in a fluid medium. They are usually thought of as Bingham-plastic fluids characterized by an apparent yield stress and viscosity. Partial substitution of the micron-sized iron particles with rod-shaped nanowires constitutes a dimorphic MR fluid. In this study, we investigate the influence that nanowires have on the magnetorheological and sedimentation properties of MR fluids. A variety of conventional and dimorphic MR fluid samples were considered for this study with iron loading ranging from 50 to 80 wt%. The nanowires used in this study have mean diameters of 230 nm and a length distribution of 7.6 ± 5.1 µm, while the spherical particles have a mean diameter of 8 ± 2 µm. Flow curves were measured using a parallel disk rheometer and a sedimentation measuring instrument was constructed for quantifying sedimentation velocity. The Bingham yield strength and sedimentation velocity of the dimorphic MR fluids are then compared to those of conventional MR fluids incorporating spherical particles.

https://iopscience.iop.org/article/10.1088/0964-1726/17/4/045022/pdf

Dimorphic magnetorheological fluids : exploiting partial substitution of microspheres by nanowires

This study addresses the feasibility and effectiveness of a self-powered magnetorheological (MR) damper using in-situ energy harvested from the vibration and shock environment in which it is deployed. To achieve this, an energy-harvesting device is designed and added to a MR damper. This energy-harvesting device consists of a stator, a permanent magnet, and a spring and operates as an energy-harvesting dynamic vibration absorber (DVA). The dynamic equation for the self-powered MR damper is derived. To evaluate the vibration isolation capability of the self-powered MR damper, a single-degree-of-freedom engine mount system using the MR damper is simulated. The governing equation of motion for the engine mount system is derived. A parametric study is conducted to find the optimal stiffness of the energy-harvesting DVA for the engine mount system. The isolation performance of the engine mount system employing the self-powered MR damper is theoretically evaluated in the frequency domain.

Self-Powered Magnetorheological Dampers

A laboratory demonstration of a hybrid magnetorheological fluid?elastomeric (MRFE) damper is investigated for adjustable or programmable lag mode damping in helicopters, so that damping requirements can be varied as a function of different flight conditions. The laboratory demonstration of this hybrid MRFE lag damper consists of a double lap shear elastomeric damper in parallel with two magnetorheological (MR) flow mode dampers. This is compared to a damper where only elastomeric materials are implemented, i.e., a double lap shear specimen. The relationship between the output force and the quasi-steady harmonic displacement input to a flow mode MR damper is exploited, where the output force can be adjusted as a function of applied magnetic field. Equivalent viscous damping is used to compare the damping characteristics of the hybrid damper to a conventional elastomeric damper under steady-state sinusoidal displacement excitation. To demonstrate feasibility, a hybrid MRFE damper test setup is designed, and single frequency (lag frequency or rotor in-plane bending frequency) and dual frequency (lag frequency and rotor frequency) tests are conducted under different magnetic fields. The hybrid MRFE damper exhibits amplitude-dependent damping behavior. However, with application of a magnetic field, the damping level is controlled to a specific damping level objective as a function of displacement amplitude. Similarly, under dual frequency conditions, damping degradation at the lag frequency, because of lag motion at the rotor frequency, can also be recovered by increasing magnetic field. A time-domain analysis is developed to study the nonlinear dynamic behavior of the hybrid MRFE damper. Using rate-dependent elasto-slides, the amplitude-dependent behavior of the hybrid MRFE damper is accurately reconstructed using both constant and current-dependent (i.e.?controllable) parameters. The analysis is physically motivated and can be applied to the elastomer and MR fluid damper components separately.

https://iopscience.iop.org/article/10.1088/0964-1726/17/4/045021/pdf

Hybrid magnetorheological fluid–elastomeric lag dampers for helicopter stability augmentation

Application of monodisperse Fe3O4 submicrospheres in magnetorheological fluids

Aircraft landing gears are subjected to a wide range of excitation conditions with conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. In part 1 of this contribution, a methodology was developed that enables the geometry of a flow mode MR valve to be optimized within the constraints of an existing passive landing gear. The device was designed to be optimal in terms of its impact performance, which was demonstrated using numerical simulations of the complete landing gear system. To perform the simulations, assumptions were made regarding some of the parameters used in the MR shock strut model. In particular, the MR fluid's yield stress, viscosity, and bulk modulus properties were not known accurately. Therefore, the present contribution aims to validate these parameters experimentally, via the manufacture and testing of an MR shock strut. The gas exponent, which is used to model the shock strut's nonlinear stiffness, is also investigated. In general, it is shown that MR fluid property data at high shear rates are required in order to accurately predict performance prior to device manufacture. Furthermore, the study illustrates how fluid compressibility can have a significant influence on the device time constant, and hence on potential control strategies.

/pdf/magnetorheological-landing-gear-2-validation-using-2s3h0jkqxd.pdf

M Rennison

Papers

Magnetorheological landing gear: 2. Validation using experimental data