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Research on Fractal Friction Model for Contact Pairs inside a Ball Joint
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
During the operation of the ball joint, its service life is affected by the internal friction. Taking the ball joint as the research object, based on fractal theory, the friction between the steel ball and the raceway, the steel ball and the cage inside the ball joint of an automotive drive shaft system is studied in this paper. During the analysis, the friction between the steel ball and the raceway is regarded as the friction between a sphere and an arc raceway surface, and the friction between the ball and the cage is considered as the friction between a sphere and a plane. In order to describe the friction state between rough surfaces more accurately, this paper proposes a method to modify the size distribution function of contact asperities between two rough planes, and obtains the size distribution function of contact asperities between the rough sphere and the rough arc raceway surface and the rough sphere and the rough plane. Then based on the modified size distribution function, the fractal models for friction coefficient of the spherical-arc cylindrical surface contact pair and the spherical-plane contact pair at different contact deformation stages are established. The contact deformation stage of the contact pair is divided into four stages: the elastic deformation stage, the first elastoplastic deformation state, the second elastoplastic deformation state and the plastic deformation state. Through numerical examples, the relationship among the friction coefficient, the real contact area and the contact load of the steel ball-raceway contact pair and the steel ball-cage contact pair is analyzed, and the influence of fractal parameters on the friction coefficient is studied.