scholarly journals Optimal Constant-Stress Accelerated Degradation Test Plans Using Nonlinear Generalized Wiener Process

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Zhen Chen ◽  
Shuo Li ◽  
Ershun Pan
Keyword(s):  
Wiener Process ◽  
Measurement Errors ◽  
Constant Stress ◽  
Normal Operation ◽  
Test Duration ◽  
Accelerated Degradation ◽  
Stress Levels ◽  
Degradation Test ◽  
Accelerated Degradation Test ◽  
Generalized Wiener Process

Accelerated degradation test (ADT) has been widely used to assess highly reliable products’ lifetime. To conduct an ADT, an appropriate degradation model and test plan should be determined in advance. Although many historical studies have proposed quite a few models, there is still room for improvement. Hence we propose a Nonlinear Generalized Wiener Process (NGWP) model with consideration of the effects of stress level, product-to-product variability, and measurement errors for a higher estimation accuracy and a wider range of use. Then under the constraints of sample size, test duration, and test cost, the plans of constant-stress ADT (CSADT) with multiple stress levels based on the NGWP are designed by minimizing the asymptotic variance of the reliability estimation of the products under normal operation conditions. An optimization algorithm is developed to determine the optimal stress levels, the number of units allocated to each level, inspection frequency, and measurement times simultaneously. In addition, a comparison based on degradation data of LEDs is made to show better goodness-of-fit of the NGWP than that of other models. Finally, optimal two-level and three-level CSADT plans under various constraints and a detailed sensitivity analysis are demonstrated through examples in this paper.

scholarly journals Optimization of the Accelerated Degradation Test Plan for Electrical Connector Contact Pairs Based on a Nonlinear Wiener Process

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Ping Qian ◽  
Lei Hong ◽  
Wenhua Chen ◽  
Yongwang Qian ◽  
Zhe Wang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Wiener Process ◽  
Stress Level ◽  
Test Plan ◽  
Accelerated Degradation ◽  
Stress Levels ◽  
Degradation Test ◽  
Accelerated Degradation Test ◽  
Stress Dependent ◽  
Drift Coefficient

Accelerated degradation test is an effective method to evaluate the reliability of products with long life and high reliability. The performance of most products fluctuates randomly in the degradation process, so it is suitable to use Wiener process. At present, the diffusion coefficient is regarded as constant in Wiener process, while the drift coefficient is related to stress. However, in practice, the amplitude of product performance fluctuation increases with the increase of stress level, which is not constant. Therefore, for the nonlinear Wiener case where both the drift coefficient and the diffusion coefficient are stress dependent, this paper studies the constant-stress accelerated degradation test theories and methods. Taking the contact pairs of electrical connectors as the research object, the minimum variance of reliable life estimate under normal stress is taken as the target. After determining the censored time at each stress level, the test stress level, the sample distribution ratio at each stress level, and the test interval at the one-third power scale of time are taken as design variables. The test plan under 3, 4, and 5 stress levels is optimized and compared with the general test plan. The influence of the difference between high and low stress levels on the evaluation accuracy is analyzed. Finally, the sensitivity analysis of parameters shows that the optimization plan has good robustness, and the change of stress quantity has little influence on the robustness of the plan.

A zero-failure accelerated degradation test under ramp–soak–stress loading

2017 ◽  
Vol 232 (3) ◽  
pp. 262-273 ◽  
Author(s):  
Preeti Wanti Srivastava ◽  
Manisha
Keyword(s):  
High Reliability ◽  
Asymptotic Variance ◽  
Optimum Number ◽  
Test Duration ◽  
Accelerated Degradation ◽  
Proposed Model ◽  
Method Of Maximum Likelihood ◽  
Optimum Plan ◽  
Degradation Test ◽  
Accelerated Degradation Test

This article deals with the design of optimal ramp–soak–stress accelerated degradation test using Wiener process for modeling degradation paths. In an accelerated degradation test, failure occurs when the performance characteristic crosses the critical value the first time. Accelerated degradation test is incorporated in zero-failure reliability demonstration test to facilitate reduction in the test duration resulting in reduction in the test cost of high-reliability items. The parameters in model are estimated using method of maximum likelihood. The optimum plan consists in finding out optimum number of ramp–soak–stress cycles, optimum number of specimens, optimum stress change point(s), and optimum stress rates by minimizing asymptotic variance of estimate of [Formula: see text] quantile of the lifetime distribution at use condition subject to the constraint that total testing or experimental cost does not exceed a prespecified budget. An example is given to illustrate the proposed model, and sensitivity analysis is also carried out.

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