The friction brake works as an indispensable guarantee for regular work and safety operation of vehicles and industrial equipments. Friction and wear behaviors of brake's friction materials are considered as an important subject. In this article, friction materials were classified by matrix categories, and their major components were introduced first. Then, the advantages and disadvantages of each friction material were summarized and analyzed. Furthermore, the microcontacting behaviors on friction interface and the formation mechanism of various friction films were discussed. Finally, the influential rules and mechanism of braking conditions (temperature, pressure, and velocity) on the friction and wear behaviors of friction materials were summarized. It is concluded that the friction film, an intermediate product in braking, is greatly beneficial to protect friction materials from being seriously abraded. The braking conditions have complicated influences on friction and wear behaviors of brake. Generally, the friction coefficient tends to be fairly low while the wear rate increases rapidly under a condition with high temperature, braking pressure, or initial braking speed.

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Aiming to improve the shear yield stress of magnetorheological fluid, magnetorheological fluids with different particle characteristics are prepared, and the influence rules of particle mass fraction, particle size, nanoparticles content and application temperature on shear yield stress are investigated. Experimental results indicate that shear yield stress increases approximate linearly with the enhancement of particle mass fraction. Particle size and the nanoparticles within 10% mass fraction can improve the shear yield stress effectively. When the application temperature is higher than 100 o C, the shear yield stress decreases rapidly because of thermal expansion and thermal magnetization effect.