Aging phenomenology and modeling

The authors review aging phenomenology and life modeling; illustrate different approaches, showing their advantages and applicability limits; and raise problems relevant to practical applications of models and evaluation of material endurance. They present the fundamentals of phenomenological aging theory and life modeling and give electrical and combined-stress life data for different materials. Electrical, thermal and multistress life models valid for insulating materials and systems, showing either linear or curvilinear behavior are presented. 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-stress life and aging models is discussed. Statistical processing of data and determination of model parameters are mentioned, and graphical methods for material characterization are proposed