Tangential contact analysis of spherical pump based on fractal theory

The tangential contact between piston and cylinder in spherical pump is investigated using both analytical method and fractal theory. The analytical model is established firstly, friction coefficient between piston and cylinder is considered. Effects of operating conditions and structural parameters are analyzed. Besides, a fractal contact model for spherical pump is proposed, and the model is validated by Jiang's general contact model and experimental results. Variation of the tangential contact stiffness with factors such as fractal dimension, characteristics length, friction coefficient, material hardness, yield stress, elastic modulus and loaded force are studied comprehensively. Results indicate these parameters have complex effects on tangential contact stiffness under different operating conditions, the related conclusions can also be utilized to analyze the tangential contact characteristics of spherical surfaces.