Effect of stress relaxation on the sealing performance of O-rings in deep-sea hydraulic systems: A numerical investigation

A reliable O-ring seal is an important guarantee for the stable running of deep-sea hydraulic systems and for the execution and completion of subsea tasks. Stress relaxation of rubber materials under deep-sea low-temperature conditions has an impact on the O-ring sealing performance, especially when coping with a sudden and sharp increase in clearance height. In this paper, the physical stress relaxation characteristics of nitrile rubber at a low temperature of 4 °C were tested. On this basis, a finite element numerical model of the O-ring sealing structure utilized in deep-sea hydraulic systems was developed. Then, the sealing performance under deep-sea conditions, together with a sharp and sudden clearance height increase, was simulated. A study on the effect of parameter changes on sealing performance was also carried out. The results show that the reliability of O-ring sealing structures in deep-sea hydraulic systems continues to deteriorate due to volume shrinkage and stress relaxation of rubber material. The seal safety margin decreases significantly when a sudden and sharp increase in clearance height occurs, and a little recovery is achieved after a long time. Compared to the standard structure, increasing the initial compression of the O-ring can effectively enhance its sealing reliability.