A Method on Life Assessment for O-Ring Seals Based on Finite Element Analysis-Assisted Compression Set Calculation

The service life of O-ring rubber seals (O-rings) are crucial for ensuring the safe operation of equipment. Compression Set (CS) is one of the key indicators characterizing O-ring seal performance degradation. In this paper, a group of accelerated degradation tests were conducted to evaluate the service life for a kind of nitrile butadiene rubber (NBR) O-rings. However, it is very hard to measure the radial CS due to irregular deformation, where radial is the main compression direction, whereas changes in axial height can be able to measure more readily and accurately. To address this issue, finite element analysis (FEA) was attempted to simulate the O-rings deformation recovery behavior after unloading from various compression durations. A hyperelastic-viscoelastic constitutive model was developed for the O-rings material, and the quantitative relationship between the post-unloading axial height and radial thickness were established. And then, the experimentally measured axial height data were converted into equivalent radial thicknesses. At last, by the radial CS obtained, the logarithmic degradation model and life extrapolation method were employed to assess the O-rings service life. The FEA-assisted approach in this paper offers an effective methodology for assessing the service life of O-rings experiencing irregular deformation.