Degradation Modeling and Lifetime Prediction Considering Effective Shocks in a Dynamic Environment

Abstract

For some design applications, the environment in actual field conditions does not remain constant but instead changes dynamically. In addition, stress levels might change sharply, and if the change happens for a long enough time and at a high enough rate, it could act as a shock to the product, although it is not actually a shock that occurs instantly. This situation is defined as an effective shock in this paper. An effective shock is caused by a rapid change in stress that has an analogous effect to an actual shock, where the stress change is immediate. Existing works on degradation modeling and lifetime prediction for products operating in a dynamic environment consider the effects of time-varying stress levels on the degradation rate of product performance. If shocks are considered at all, it is only those shocks that occur instantaneously. In this paper, a model that characterizes the degradation process of a product operating in a dynamic environment considering effective shocks is proposed to predict the residual lifetime of the product. This model is established based on a stress-dependent degradation rate and an effective shock function together with a Wiener process to model the stochastic degradation. A simulation study is presented as a demonstration of the application of this model, and a case study testing miniature light bulbs is presented to verify the effectiveness of the proposed model.