Reliability Evaluation Based on Sequencing of Applied Stresses

In probabilistic reliability analysis, it is common that the models relating time to failure with environmental stresses are insensitive to the sequence of the stress level application. For a step-stress model, this means that the probability of failure is a function of the exposure time at each stress and it is unaffected by the order of stress application. These models may lead to improper reliability evaluation since it has been shown in fatigue analysis and similar areas that the stress sequencing effect may be substantial. However there is limited discussion about this topic in the reliability field. The purpose of this paper is to bridge the relationship between cumulative damage concepts in fatigue analysis and modeling and prediction of reliability. We also discuss and present reliability models and conditions where the reliability estimation model is insensitive to the sequence of the applied stresses.