Life models for insulating materials in combined-stress conditions

In the paper, single-stress electrical and thermal models for life prediction of electrical insulating materials are presented as a basis for the derivation of combined-stress models, both for threshold and nonthreshold materials. A critical analysis of these models allows the definition of the concept of threshold and nonthreshold material behaviour, as well as the attainment of a new general combined-stress model, valid for all materials, irrespective of the existence of a threshold at room temperature