Reliability Evaluation Method for Accelerated Degradation Test based on Nonlinear Gamma Process

The accelerated degradation test (ADT) has been extensively applied to the reliability evaluation of complicated products with high reliability, and small sample size. During the ADT, products exhibit nonlinear performance degradation and coupled competing failure that are originating from multiple performance parameters. Nevertheless, these situations have been scarcely reported in the existing works in the literature, resulting in the low-reliability evaluation accuracy. Along these lines, to solve this problem, a reliability evaluation method for ADT based on the nonlinear Gamma process was displayed in the work. More specifically, to effectively address the nonlinear performance degradation in the ADT, a nonlinear Gamma model based on the time conversion function was constructed, and a model analysis method based on the maximum likelihood function was alsoadvised. By consideringthe coupled competing failures of multiple performance parameters, the coupled competing failure models based on the Copula function were also constructed. Furthermore, the solving and optimization methods of the models were proposed and the universal reliability acceleration model of products was established to systematically evaluate the reliability under normal service stress loads. Finally, a reliability evaluation of a driver mode was conducted. The acquired results were compared with the traditional method without consideration of the coupled competing failures of multiple performance parameters. From our analysis, a greater evaluation accuracy of the proposed method compared to the traditional method was verified.