O-ring is a commonly used sealing device for cylinders, and its sealing and friction properties play a significant role in the stable movement and precise control of the cylinder. The research on O-ring seals includes reliability analysis, selection of sealing ring structural parameters, distribution of contact stress, lubrication and friction characteristics, and other related theoretical studies. This article focuses on the mathematical modeling and simulation analysis of the stress field, temperature field, grease lubrication characteristics, and friction characteristics of a single-sided restricted O-ring seal.
A two-dimensional axisymmetric finite element analysis model of FESCO cylinder O-ring was established in ANSYS. By analyzing the influence of preloading shrinkage and driving chamber gas pressure on contact stress and Von Mises stress, it was found that the O-ring can achieve reliable static sealing when the preloading shrinkage is greater than 10% and the driving chamber pressure is lower than 0.5 MPa. When there is relative sliding in the O-ring, based on the previous structural field, the heat source is attributed to frictional heating and mechanical hysteresis heating, and temperature field analysis is conducted. Considering the influence of temperature on contact stress, a secondary coupling is achieved using structure heat structure. It is found that the limited increase in temperature in the contact zone has a small impact on the contact stress of the O-ring, and the decisive factor affecting the dynamic and static sealing performance of the O-ring is the pre compression amount of the O-ring.
A mathematical model was established for O-ring and cylinder under grease lubrication conditions, including Reynolds equation, film thickness equation, load balance equation, and energy equation. Multi grid numerical integration was used to improve the convergence of the entire iteration. The variation trends of lubrication film thickness and friction force of grease with relative sliding speed, compression rate, and gas pressure were calculated through C programming. The simulation results indicate that gas pressure has a relatively small effect on film thickness, but has a significant impact on contact stress. The relative sliding speed has the greatest impact on film thickness and has a relatively small impact on the distribution of contact stress. The film thickness in the contact center area is between 1-2 μ m, which can achieve complete lubrication.
Establish a sliding contact friction model between O-ring and cylinder, simplify the constitutive equation of rubber material and rough rigid surface, derive the mathematical model of hysteresis friction force of O-ring rubber sliding on sinusoidal surface and randomly rough parting surface of cylinder, and build a simulation model in Matlab. The increase in relative sliding speed and gas pressure will lead to an increase in hysteresis friction, with sliding speed playing a dominant role. When the sliding speed is between 0.1m/s and 0.5m/s, the relationship between the hysteresis friction coefficient and the relative velocity is approximately a quadratic parabolic relationship. The obtained variation law has certain engineering value for predicting cylinder friction force.
Keywords: O-ring seal; Contact stress; Rubber friction; Finite Element Method
