Development of a magnetorheological brake with a slotted disc

Abstract

A conventional disc wears out and the brake pollutes the environment. Brake pad dust is reported to be the largest source of environment pollution 1 . The particles emanating because of wear of the brake pad pollute the environment 2,3,4 . In addition to pollution caused by wear particles, the friction-induced noise between the brake pad and the disc is also a major concern 5 . Also, localized heating occurs in a conventional disc brake. To tackle both of these problems, conventional disc brakes can be replaced with manetorheological fluid brakes. Magnetorheological fluids are materials having a shear yield stress which is a function of the magnetic field. On the application of a magnetic field, magnetorheological particles become aligned and increase the shear resistance between relatively moving surfaces. The friction between the stator and the rotor increases and fulfils the braking function, which means that magnetorheological fluids can be used as brake friction materials. A magnetorheological brake consists of a rotating disc or discs immersed in a magnetorheological fluid and enclosed in an electromagnetic casing. The torque characteristics of the magnetorheological brake in the shear mode are controlled by regulating the yield stress of the magnetorheological fluid. An increase in the yield stress increases the braking torque, which means that, the higher the yield strength of the magnetorheological fluid, the better is the performance of the magnetorheological brake. However, the major disadvantage of the shearmode-based magnetorheological brake is its high resisting torque even in the off-state viscosity, and such magnetorheological brakes cannot be recommended for automotive applications. To obtain the performance of a conventional disc brake, experimental studies on a conventional disc brake were performed using a full-scale dynamometer. In addition to wear particles, localized heating of the disc was observed. The disc-pad interfaces were modelled to simulate the disc temperature. The values of the maximum temperature, which were obtained from simulations as well as experiments, were compared. The simulations were extended to hypothetical 360°pads, and a significant reduction in the maximum temperature was noted. Based on the idea of 360°pads, a magnetorheological brake subjected to shearing was analysed.To perform experiments on a small-scale magnetorheological brake, a test set-up was designed and developed, and it was confirmed that a magnetorheological brake subjected to shearing provides a better torque than does a conventional disc brake of the same size. An ideal magnetorheological brake should exert a zero frictional torque in the off-state condition and a controllable frictional torque in the on-state condition. An attempt was made to design such a magnetorheological brake. To overcome the disadvantage of the shear-mode-based magnetorheological brake, a new design of magnetorheological brake with a slotted disc was proposed. The design and development of the proposed magnetorheological brake...

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