Magnetorheological fluid

About: Magnetorheological fluid is a research topic. Over the lifetime, 8538 publications have been published within this topic receiving 131502 citations. The topic is also known as: MRF & MR fluid.

Design and Experimental Evaluation of a Magnetorheological Brake

Abstract: A new magnetorheological (MR) brake prototype was designed, fabricated and tested. Firstly, the rheological properties of MR fluids, in particular the dynamic yield stress, were experimentally investigated based on a Bingham plastic model. The working principles of the MR brake were then analysed and discussed. The equations for transmitted torque were derived and used to evaluate the disc-shaped MR brake. This was followed by an analysis of an electromagnet using the finite element method. Following the manufacturing and fabrication of a brake prototype, the mechanical performance of the MR brake was experimentally evaluated with a specially designed test rig. The effects of magnetic field and rotary speed on the transmitted torque were addressed, and an amplifying factor was introduced to evaluate the brake performance. It was found that brake torque increased steadily with the increment of magnetic field or rotary speed. The amplifying factor showed an increasing trend with the magnetic field but a decreasing trend with rotary speed.

A novel hysteretic model for magnetorheological fluid dampers and parameter identification using particle swarm optimization

Abstract: Non-linear hysteresis is a complicated phenomenon associated with magnetorheological (MR) fluid dampers. A new model for MR dampers is proposed in this paper. For this, computationally-tractable algebraic expressions are suggested here in contrast to the commonly-used Bouc–Wen model, which involves internal dynamics represented by a non-linear differential equation. In addition, the model parameters can be explicitly related to the hysteretic phenomenon. To identify the model parameters, a particle swarm optimization (PSO) algorithm is employed using experimental force–velocity data obtained from various operating conditions. In our algorithm, it is possible to relax the need for a priori knowledge on the parameters and to reduce the algorithmic complexity. Here, the PSO algorithm is enhanced by introducing a termination criterion, based on the statistical hypothesis testing to guarantee a user-specified confidence level in stopping the algorithm. Parameter identification results are included to demonstrate the accuracy of the model and the effectiveness of the identification process.

Rheological properties of magnetorheological fluids

Abstract: The effects of dispersed phase saturation magnetization and applied magnetic fields on the rheological properties of magnetorheological (MR) fluids are described. MR fluids based on two different grades of carbonyl iron powder with different average particle size, 7–9 μm (grade A) and 2 μm (grade B), were prepared. Vibrating sample magnetometer measurements showed that the saturation magnetization values were 2.03 and 1.89 T for grades A and B, respectively. Rheological measurements were conducted for 33 and 40 vol% grade A and grade B based MR fluids with a specially built double Couette strain rate controlled rheometer at flux densities ranging from 0.2 to ~0.8 T. The yield stresses of 33 and 40 vol% grade A were 100 ± 3 and 124 ± 3 kPa, respectively at 0.8 ± 0.1 T. The yield stress values of MR fluids based on finer particles (grade B) were consistently smaller. For example, the yield stresses for 33 and 40 vol% grade B based MR fluid were 80 ± 8 and 102 ± 2 kPa, respectively at 0.8 ± 0.1 T. The yield stresses at the flux density approaching magnetic saturation in particles (B ~ 0.8T) were found to increase quadratically with the saturation magnetization (μ0Ms) of the dispersed magnetic phase. This is in good agreement with the analytical models of uniformly saturated particle chains developed by Ginder and co-workers. The results presented here show that the decrease in yield stress for finer particle based MR fluids is due to the relatively smaller magnetization of the finer particles.

Investigation on magnetorheological elastomers based on natural rubber

Abstract: Magnetorheological Elastomers (MR Elastomers or MREs) are a kind of novel smart material, whose mechanical, electrical, magnetic properties are controllable under applied magnetic fields. They have attracted increasing attentions and broad application prospects. But conventional MREs are limited to wide applications because their MR effects and mechanical performances are not high enough. This paper aims to optimize the fabrication method and to fabricate good natural rubber based MREs with high modulus by investigating the influences of a variety of fabrication conditions on the MREs performances, such as matrix type, external magnetic flux density, and temperature, plasticizer and iron particles. Among these factors, the content of iron particles plays a most important contribution in shear modulus. When the iron particle weight fraction is 80% and the external magnetic flux density is 1 T, the field-induced increment of shear modulus reaches 3.6 MPa, and the relative MR effect is 133%. If the iron weight fraction increases to 90%, the field-induced increment of shear modulus is 4.5 MPa. This result has exceeded the best report in the literatures researching the MREs on the same kind of matrix. The dynamic performances of MREs were also experimentally characterized by using a modified Dynamic Mechanical Analyzer (DMA) system. The effects of strain amplitude and driving frequency on viscoelastic properties of MREs were analyzed.

Magnetorheological fluid devices

Abstract: Magnetorheological (MR) fluid dampers (16) are optimized. Dimensional relationships involved in the flow of magnetic flux are related to an operational parametric ratio of magnetic flux density in the fluid to the flux density in the steel. A magnetic valve (30) is utilized to change the flow parameters of the MR fluid and, hence, the operational characteristics of the damper (16). Several embodiments depicting improved piston designs, including spool as well as toroidal configurations, are disclosed. In addition, both single (16) and twin-tube (16) housing designs are presented, along with several sealless designs. Baffle plates (50) and toroidal magnetic segments (40) interspersed with flow slots (56) are utilized to increase contact between the fluid and the magnetic coil (40).