Research On Friction And Wear On The Rough Surface Of Brake Disc-Brake Pad Based On Fractal Theory

With the rapid development of the global automobile field,China’s automobile industry is developing very fast,followed by more traffic accidents,so the safety of vehicles is increasingly important.Vehicle safety is mainly reflected in the performance of brake disc and brake pad,from the microscopic observation of the surface of brake disc and brake pad is rough.And rough surface morphology characteristics and its contact characteristics is the fundamental cause of friction and wear and friction heat surface.When the two rough surfaces contact and slide under the action of pressure,the tiny particles are separated from the contact surface under the effect of friction,which causes the surface material loss,dimensions change,mass loss and surface damage.So it is necessary to study the contact property and friction mechanism of fractal rough surface.In this paper,rough surfaces are characterized based on fractal theory,and numerical simulation analysis method is used to study the real contact area,maximum contact stress,friction and wear,and friction temperature on fractal rough surfaces of objects with the change of contact state.The specific work is as follows:(1)Based on fractal theory and W-M equation,two-dimensional and three-dimensional models of rough surface were established successively to analyze the influence of different fractal dimensions and characteristic scale coefficients in W-M equation on the characterization of fractal rough surface.(2)Based on the obtained rough surface data files,a solid model of rough surface was established,and the contact model of the smooth surface on the brake and the rough surface on the disc was defined.The influence of different normal loads,fractal dimensions and characteristic scale coefficients on the contact stress and real contact area of brake disc-brake pad was analyzed.(3)The rough-rough model of brake disc and brake pad was established to analyze the contact stress,the real contact area and the wear area proportion of the rough surface of brake pad at different times.The friction coefficient influence on the real contact area of different degree of roughness brake pads was researched.(4)The temperature field analysis of the brake disc-brake pad model is carried out,and the effects of fractal dimension,relative sliding speed and applied load on the flash point temperature during rough surface braking are studied.The friction and wear characteristics of the brake pad and its influencing factors under the consideration of the surface microstructure are obtained through analysis,which provides a theoretical basis for the design of the brake pair.