Planning of Partially Accelerated Degradation Test with Two Stress Variables for Practical Lifetime Estimation

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.

Strategic Approaches for Assessing the Reliability Information during Product Development: Perspective of the Partially Accelerated Degradation Test

“…On the other hand, the PADT properly uses the degradation data to assess the reliability information without failure. The research articles that have utilized this advantage are Lim et al [4], Kim and Sung [5], and Kim et al [6].…”

“…According to Lemma 1 in Kim et al [6], 20 units are allocated to the V&V tests under the normal use condition, the high-temperature operating life (HTOL) under the maximum temperature and the normal use voltage, the voltage limit tests under the normal use temperature and maximum voltage, and the biased highly accelerated stress test (HAST) for the combination of the maximum stress levels. In other words, 80 units among the 3000 samples are used to estimate the prior information for the acceleration model parameters.…”

“…Based on the estimated results, four units are added to the V&V tests under the normal use condition and 457, 557, and 92 units are allocated for the voltage limit test, the HTOL, and the HAST, respectively. A total of 1810 units are tested under the middle-stress levels, which are calculated based on model assumption 4 in Kim et al [6]. In the semiconductor area, qualification tests should be used to verify the various item requirements.…”

“…While prior information is essential for designing classical accelerated test plans, this research presents a method for obtaining prior information on the lifetime model parameters while also obtaining V&V test results and reliability information on the product. The degradation path and acceleration models with standardized stress variables related to this research are presented through illustrative examples, utilizing existing PADT articles [4][5][6][7].…”

Reliability and Lifetime Assessment of Glider Wing’s Composite Spar through Accelerated Fatigue Life Testing

“…Studies on accelerated life testing can be divided into several main directions: developing hypotheses and statistical models necessary for estimating reliability indicators and confidence intervals [3]; optimization of models and accelerated test plans [4][5][6]; accelerated fatigue tests used on different industrial materials and products [7][8][9][10][11][12]; and the extension of the scope of application of accelerated testing techniques on various industrial products [13][14][15][16][17]. The extremely varied and complex stresses applied to the aerospace components have led to experimental studies, in order to ensure the proper functioning and the required reliability under maximum stress regime, at a minimum material and labour use.…”