| In this paper the growth of crack in friction surface of brake lining and its influence on friction and wear performance are investigated. It is shown by the comparison of wet mixing method and dry mixing method for that the friction material made by wet mixing method has higher friction coefficient and lower wear rate than the friction material made by dry mixing method, the wet-mixed material has less surface cracks than the dry-mixed material at the temperature higher than at 300℃. With the temperature rising, friction surfaces made by both methods have more cracks and the sizes of the cracks are bigger. At first the surface cracks of friction material are not obvious in the temperature lower than 200℃, and there are a few cracks began to appear at 250℃, and the cracks began to increase and expand at 300℃and start to expand in large area at 350℃. Same phenomena for crack growth appear by increasing the speed and the pressure in the friction surface.It is found that the influence of cracks on the friction performance is dual. When the cracks in the friction surface are tiny, they can increase friction coefficient, and reduce wear rate, and when the cracks in the friction surface propagate in certain amount, they can decrease friction coefficient, and increase wear rate. It is indicated by using steel fiber and rubber compound material that the crack growth can be restrained by using steel fiber, and it can be promoted by increasing rubber compound material. Therefore the crack appearance and its growth can be controlled by using both steel fiber and rubber compound material, resulting in improvement of friction performance, and the optimal content of rubber compound material is 20%. |
