Study on characteristics and mathematical models of stress relaxation for metal O-rings

Abstract

The metal O-ring is effectively applied to extreme conditions and long-term uses for several decades, where conventional seals cannot meet the requirements. During the long-time service, the stress relaxation of the metal O-ring has been confirmed to be a potential damage to the sealing performance. By analyzing the sealing mechanism and the problem of the stress relaxation of the metal O-ring, a model has been developed to study its stress relaxation. The model includes the contact model, the stress–strain model, and the dynamic equation of stress relaxation. Based on the classical elastic-plastic model for two contact rough surfaces, the contact model of sealing zone is developed, by which the mechanical and geometric parameters of the sealing zone can be obtained for the initial state after the assembling. In the stress–strain model, the determination of stress and strain in the metal O-ring is performed by means of a simplified closed-form solution. The dynamic equation of stress relaxation using the stress-creep rate equation is developed, and is solved by combination of the contact model and the stress–strain model. The equation can be adopted for stress relaxation analysis of the metal O-ring at any time. After a validation of the model by comparison with experiments, a parametric study is presented. Simulation results corresponding with the mathematical models explain how the stress relaxation characteristic of the metal O-ring is influenced by a number of parameters.