Estimation of Product Lifetime Considering Gamma Degradation Process with Multi-Stress Accelerated Test Data
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Consideration of degradation behavior for estimating reliability provides a better understanding and visualization of product failure processes. Certainly, the accelerated degradation test methods have proven to be very effective to estimate lifetime, especially for highly reliable products. To model degradation behavior, the most of the earlier work has assumed linear degradation considering single stress variable or failure process. However, in reality the product is subjected to multiple non-linear failure processes that influence the propagation of each other causing to accelerate the failure processes in general. In this work, we attempt to model multiple non-linear failure processes. The gamma process is considered to model the degradation process using accelerated degradation test data. Further, to capture the field behavior, this work assumes both the gamma parameters are dependent on stress variables, the fact that has been ignored in most of the existing literature. Model parameters are estimated using maximum likelihood estimation (MLE) approach. Finally, the gamma parameters are estimated under normal operating conditions to provide a lifetime estimate using the appropriate stress-life relationship. The methodology has been demonstrated by the accelerated degradation data of LED bulbs.
