| The braking interface of high-power wind power brake pads and brake discs is a rough surface composed of a series of irregular micro-convex bodies.Therefore,in the actual sliding-friction process,the contact portion is much smaller than the nominal contact area.It leads to a large load on the contact area of the asperity.In the process of friction,the nonuniform· distribution of heat and the formation of local flash temperature cause changes in the properties of the friction pair material,which seriously affects the reliability and service life of wind power brakes.If the microscopic process of frictional contact during braking is deeply studied,the force-heat distribution of the contact surface of the friction pair is effectively predicted.Further to improve the work performance of friction pair,it provides theoretical basis to improve the service life of wind power brakes.The microscopic geometric model of brake pads and brake discs for wind power brakes based on fractal theory is built in this paper.Combined with the high-speed and heavy-duty braking conditions of high-power wind power brake,the microscopic friction mechanism of the model in different wear stages of the brake disc is analyzed.The main researches are listed as follows:(1)High-power wind power brake disc friction wear process is divided into three stages:initial wear,stable wear and rapid wear.Based on the fractal theory,the wind power brake pads and brake discs rough and microscopic surface topography are generated.The 3D microscopic model of brake pads and brake discs for wind power brake is constructed.Combining the evaluation criteria of surface roughness,the rough surface reference line equation is solved.The arithmetic mean deviation of the contour of the rough surface Ra and the maximum height of the contour Rz are calculated.(2)Combining high-power wind power brake braking conditions,ABAQUS is used to establish micro friction model of brake interface in initial wear stage for simulation and analysis.The temperature distribution,contact pressure and contact stress of the microscopic model of the brake pads and brake discs in the initial wear stage is obtained.By changing various braking parameters,the temperature curve,contact pressure curve and stress curve of the contact area of the braking interface are comparatively analyzed.The microscopic friction mechanism of the wind power brake interface is revealed in the initial wear stage.(3)The finite element model of the brake interface of the wind power brake during the steady wear stage is established.The changes of the temperature,maximum contact pressure and contact stress of the micro-model of the brake pad with applied load,speed and fractal dimension is obtained at this stage.It reveals the uneven distribution and time course of changes of temperature field,pressure field and stress field during the sliding friction stage of rough surface.The effects of the formation and distribution of hotspots at this stage on contact pressure and contact stress are thoroughly studied.It explores the microscopic friction mechanism of the wind power brake interface during the steady wear stage.The research results of this paper reveal the microscopic friction mechanism of the brake interface during the braking process of wind power brakes.It is important to study the contact characteristics of the friction brakes in wind power brakes during braking process.It lays a good foundation for further study of the friction and wear mechanism of the brake interface ofwind power brakes and study of the evolution law of the third body. |
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