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The reliability information for novel products and specimens available for various tests is limited during the development stage. In many real cases, the results of general tests under use and the maximum stress levels for checking performance and design are not utilized to obtain reliability information. To solve these problems, this paper proposes a practical partially accelerated degradation test (PADT) plans with two stress variables using a two-phase strategy. In addition, a sample scenario is introduced to demonstrate the feasibility of the proposed procedure. In the first phase, the ratios of the specimens used and the maximum stress levels for each variable are determined to estimate the parameters of an accelerated model based on the D-optimality criteria. To estimate the lifetime information and check the curvature effects of the accelerated model, practical PADT plans are developed in the second phase with three stress levels for each variable, which are based on the compromise concept. In this phase, the ratios for all test points and the middle-stress levels for two variables are determined. This information is used to minimize the asymptotic variance of the maximum likelihood estimator for the q-th quantile of the lifetime distribution under the use conditions. Thus, more accurate lifetime information and model validity can be obtained when using practical PADT plans. Finally, the statistical efficiency of the proposed test plan is demonstrated in a sample scenario. [ABSTRACT FROM AUTHOR]

Because of the existence of uncertainty measurement in the process of bearings degradation, it is difficult to carry out the reliability analysis. The random performance degradation model is used to analyze the reliability life of high-speed train bearing with the characteristics of slow degradation process and relatively stable degradation path. The unknown coefficients are viewed as random variables in the model. According to the analysis to a bearing testing data, the reliability analysis of the bearing life is finally completed. The results show that the method can assess reliability of the bearing life with zero failure by taking full advantage of the performance degradation data in the small sample size. [ABSTRACT FROM AUTHOR]