https://ro.uow.edu.au/cgi/viewcontent.cgi?article=3667&context=eispapers

MR damper and its application for semi-active control of vehicle suspension system

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.

Design and Experimental Evaluation of a Magnetorheological Brake

Magnetorheological (MR) fluids are a class of new intelligent materials whose rheological characteristics change rapidly and can be controlled easily in the presence of an applied magnetic field. The devices based on MR fluids, including dampers, brakes, clutches, polishing devices and hydraulic valves, etc., have a very promising potential future; some of them have been used commercially in engineering applications such as automobiles, polishing machines, exercise equipment, etc. In this paper, the modes of operation of MR fluid devices are analysed. A comprehensive review is then presented of the principles, characteristics and engineering applications of the MR fluid devices (especially dampers) studied in the last decade. Finally, the application prospects of MR fluid devices are discussed.

Magnetorheological fluid devices: Principles, characteristics and applications in mechanical engineering

Analysis and design of a cylindrical magneto-rheological fluid brake

This paper presents a case study of magnetorheological (MR) and electrorheological (ER) valve design within a constrained cylindrical volume. The primary purpose of this study is to establish general design guidelines for volume-constrained MR valves. Additionally, this study compares the performance of volume-constrained MR valves against similarly constrained ER valves. Starting from basic design guidelines for an MR valve, a method for constructing candidate volume-constrained valve geometries is presented. A magnetic FEM program is then used to evaluate the magnetic properties of the candidate valves. An optimized MR valve is chosen by evaluating non-dimensional parameters describing the candidate valves' damping performance. A derivation of the non-dimensional damping coefficient for valves with both active and passive volumes is presented to allow comparison of valves with differing proportions of active and passive volumes. The performance of the optimized MR valve is then compared to that of a geometrically similar ER valve using both analytical and numerical techniques. An analytical equation relating the damping performances of geometrically similar MR and ER valves in as a function of fluid yield stresses and relative active fluid volume, and numerical calculations are provided to calculate each valve's damping performance and to validate the analytical calculations.

https://iopscience.iop.org/article/10.1088/0964-1726/13/6/004/pdf

Volume-constrained optimization of magnetorheological and electrorheological valves and dampers

The behavior of actuators based on magnetorheological fluids is determined by a variety of parameters. The magnetorheological properties of the MR suspension, the working mode (shear mode, flow mode, squeeze mode) and the design of the magnetic circuit consisting of MR fluid, flux guide and coil all considerably influence the properties of the actuator. This paper presents design rules for MR fluid actuators in different working modes. The behavior of MR fluids in the three working modes was investigated by using a rotational viscometer, a flow mode damper and a new measuring technique working in the squeeze mode. The measurement results for various magnetic flux densities are reported and the results of the different working modes are compared. High dynamic damping forces dependent on the magnetic field can be achieved especially in the squeeze mode. The design of the magnetic circuit of an MR fluid actuator is analyzed by using finite-element-methods. The advantages of integrating permanent magnets into the magnetic circuit of an MR fluid actuator are pointed out. The working point of the actuator can be adjusted by permanent magnets without consuming any power and the maximum power required to drive the actuator can be reduced. From these results design rules for MR fluid actuators are developed.

Design rules for MR fluid actuators in different working modes

Magnetorheological (MR) fluids can be used to construct electrically controllable dampers for a wide variety of applications. Long-stroke dampers for high vibration amplitudes usually work in the flow mode. They contain MR fluid valves to modify the flow resistance of the fluid and thus the damping force of the actuator. Due to the high vibration amplitudes the MR fluid works in the post-yield area and its viscous behavior dominates. At high piston speeds extremely high flow velocities and shear rates can occur, which reduce the MR effect. At high shear rates the damping under the influence of a magnetic field is nearly independent of the piston speed, whereas the zero field damping force still increases. Low-stroke dampers can be implemented in the squeeze mode. By increasing the magnetic control field a transition from a viscous behavior to a viscoelastic behavior can be observed, which has a strong influence on the energy dissipated by the damper and on the damping force.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ralf Boelter

Papers

Design rules for MR fluid actuators in different working modes

Performance of long-stroke and low-stroke MR fluid dampers