Fractal Simulation And Contact Features Of Rough Surfaces In Line Contact

Surface pitting and surface scuffing failures of high-speed heavy gears frequently occur in machines with the development of high-speed and heavy load machines. The conventional calculation methods of contact fatigue strength of gears have many shortcomings. Therefore, it is necessary to find an accurate way to predict the load capacity of gears, in order to prevent surface pitting and surface scuffing failures and ensure that gears can be fully exploited within the range of the allowable load. In addition, the electrical pitting failures frequently occur in gears of electrification devices and have caused huge economic losses. Therefore, it is also essential to study the electrical contact of rough surfaces and take effective measures to prevent electrical pitting failures.In part 1, the research background and engineering significance of study of contact problems of rough surfaces were introduced. The research of simulation of rough surfaces, contact models of rough surfaces and electrical contact of rough surfaces at home and abroad were reviewed. At last, the main points of this thesis were proposed.In part 2, a method of superposition of two W-M functions, respectively in the directions of x and y, for the fractal simulation of rough surfaces with different surface topography only in two mutually perpendicular directions was presented. The rough surface textures can be effectively controlled with the changes of the fractal dimension and feature scaling constant. The influences of fractal dimension and feature scaling constant on surface topography were analyzed.In part 3, elastic and elastic-plastic fractal contact models of contact between two rough surfaces were established. Based on these two models the contact pressure distribution, the real contact area and the von Mises stress distribution of the contact between two rough surfaces were obtained. Both the contact pressure distribution and the von Mises stress distribution of rough surfaces and smooth surfaces, and the real contact area and the nominal contact area were comparativelycomputed. The influences of contact behaviors between two rough surfaces and surface topography on surface contact fatigue strength were analyzed.In part 4, the contact resistance model with rectangular spots of rough surfaces was proposed based on elastic-plastic fractal contact model of rough surfaces. The influences of contact load, fractal parameters and the material of rough surfaces on the real contact area and contact resistance were analyzed. The mean contact pressure, the mean current density and the current density of a single contact spot were calculated. The quantitative relationship between the mean contact pressure and surface roughness, contact resistance and surface roughness as well as that between current density and surface roughness are studied under a fixed load.Finally, the main work and conclusions of this thesis were summarized, and the shortcomings of the research work and other important issues, which need to be studied in the future, were presented.