Reliability analysis of rubber O-rings used in the rockets

The prediction of reliability for rubber O-rings used in the rockets is of great significance for the life assessment of the rockets. In this paper, rubber O-rings were aged under accelerated conditions at temperatures ranging from 60°C to 80°C. And a new model based on Wiener process with a time scale transformation was presented to describe the degradation of CS (compression set) which is the characteristic parameter for rubber O-rings. Due to the appearance of implicit data in the presented model, EM (Expectation Maximization) algorithm was adopted to estimate the model parameters. It was proved that the EM algorithm was not only insensitive to initial guesses of the model parameters but also could achieve quick convergence. Further, combined with the degradation model and the failure threshold, the reliability curve under normal temperature storehouse was gained.