Abstract
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.
Highlights
The functions of products have steadily increased and become more complex due to advances in technology and intense market competition
In this paper, to overcome the challenges described above, which include a low prototype quantity, the disadvantages of PALT, and the lack of prior information, we proposed a strategical approach for a constant stress-partially accelerated degradation test (CS-PADT) with two stress variables based on the Wiener process (WP)
The optimal specimen ratios for four test points, which are a combination of the use and the maximum stress levels with two stress variables, are equal to 0.25 based on D-optimality criteria
Summary
The functions of products have steadily increased and become more complex due to advances in technology and intense market competition. Failures are rarely observed as the reliability of novel products has steadily improved These products are tested under general use conditions. In this paper, to overcome the challenges described above, which include a low prototype quantity (i.e., a lack of test samples), the disadvantages of PALT, and the lack of prior information, we proposed a strategical approach for a constant stress-partially accelerated degradation test (CS-PADT) with two stress variables based on the Wiener process (WP). The parameters of an acceleration model are estimated by developing the CS-PADT plans with four test points These test points are a combination of use and maximum stress levels for each stress variable and are based on the D-optimality criteria. A practical PADT plan, which uses the stress levels of the first phase and the middle-stress conditions for two stress variables, is developed to examine the validity and curvature effects of the acceleration model.
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