A Bayesian accelerated degradation studies on nitrile rubber O-ring

To research nitrile rubber O-rings' lifetime with less time and resources, and to reach a more convincing and statistic result, an accelerated degradation testing (ADT) is designed, which consists of a 90C pre-test and a step-stress test with 70 °C, 80 °C, 90 °C and 100 "C. Compression sets obtained from ADT are analyzed as degradation data, and degradation models were fitted to data using Bayesian method which easily accommodated uncertainties in the test. Then a relationship model between degradation model and temperature was built with support vector machines (SVM), so the step-stress data can be converted to data at 25°C and the O-rings' 25 °C degradation models were obtained. Finally, with these models, nitrile rubber O-rings' lifetimes were studied by Bayesian method, and the lifetime's distribution was obtained, which predicted that the nitrile rubber O-ring will reach 60% compression set by 6.2 years at 25°C based on 97.5% confidence bands.