Multistage Fractal Analysis of Contact and Porosity Evolution in Mechanical Seal Interfaces Under Varying Pressures

Abstract

The three-dimensional topography of mechanical seal end faces is characterized using the Weierstrass–Mandelbrot function, and a rough-surface contact fractal model is established with fractal dimension D_s, fractal roughness parameter G, and maximum micro-asperity contour base size l as the modeling parameters. The deformation criteria of micro-asperities are considered for elastic, elastic–plastic, and fully plastic deformation, and the initial porosity of the sealing interface is derived. The effects of contact pressure and fractal parameters on the real contact area, contact proximity, and interface porosity are analyzed. The results show that increasing contact pressure increases the real contact area and contact proximity. When D_s < 2.45, variations in G have a limited effect on these parameters, whereas when D_s > 2.45, increasing G significantly promotes their growth. The initial porosity increases with increasing D_s and is essentially independent of G, whereas loading reduces porosity, with a more pronounced reduction at higher D_s and lower G. The surface morphologies of YG8 rotating rings and M106K stationary rings were measured using an AF-LI profilometer, and their fractal parameters were determined by the structure function method. Leakage experiments under different surface morphologies, medium pressures, and contact pressures were conducted to validate the proposed model. The experimental and theoretical results exhibited consistent variation trends, demonstrating the applicability of the proposed model for predicting leakage characteristics of mechanical seal interfaces.