AGING PHENOMENOLOGY AND MODELING

This paper reviews aging phenomenology and life modeling, illustrates different approaches, showing their advantages and applicability limits and raises problems relevant to practical applications of models and evaluation of materials endurance. It deals with the fundamentals of phenomenological aging theory and life modeling, and shows a collection of electrical and combined-stress life data for different materials. Electrical, thermal and multistress life models are presented, valid for insulating materials and systems showing either linear or curvilinear behavior. Particular attention is given to threshold-life models under combined thermal-electrical stresses. General aging equations for single and multiple stresses are presented, and the life surface for combined thermal-electrical stresses is introduced. Generalization to N stresses of life and aging models is discussed. Finally, statistical processing of data and determination of model parameters are mentioned and graphical methods for material characterization are proposed.