Reliability assessment based on proportional degradation hazards model

Proportional hazards model is introduced into dealing with accelerated degradation test data, and a model based on proportional degradation hazards model (PDHM) is proposed, the only assumption is that the logarithm of the degradation hazard function is a linear function of the stress covariates. The PDHM is established with degradation data, then the probability density function and Likelihood function of the model are derived, and maximum likelihood estimate (MLE) and Newton-Raphson method are utilized to estimate the model parameters. According to the relationship between failure threshold and degradation measure, the reliability model of the product is established, with which the reliability is assessed. The model in this paper is demonstrated correct and valid by assessing the reliability of percent increase in resistance over time of carbon-film resistors.