AGING IN WIRE INSULATION UNDER MULTIFACTOR STRESS

A fundamentally based chemical-thermo dynamic multifactor stress aging functional relation requiring experimentally based constants is devel oped, based upon various theoretical models. The specific example pres ented is that for 120 V aromatic polyimide insulated wire. The stresse s of water, temperature, and mechanical strain are included and electr ical stress is considered. The results of over 2000 specimens are fitt ed to the theoretical trends. For a single independent variable functi on, the resulting relation reduces to the classical Arrhenius curve. T he three independent variable relations presented here is applied to d ata from laboratory aging experiments that simulate insulation deterio ration occurring in actual aircraft service experience. The results us ed in age categorization of US Navy aircraft are generated from wire s pecimens taken from active aircraft. The paradigm does not use ab init io based constants because of uncertainties in the theoretical develop ment, two forms of which are presented; It is the aim of this presenta tion to provide a plausible, intuitively meaningful syllogism having e lements transferable to other insulation materials/devices/systems, Th at transfer will require proper recognition of specific chemical mecha nisms in the life calculation routine, constrained by practical second ary effects and the need of nonstandard statistics.