R. F. Fedors

A failure model for sealed nickel-cadmium batteries

A model has been developed to describe failure in electrochemical batteries. The model is based on the concept of the existence and subsequent growth of flaws which ultimately lead to battery failure. This model provides, in a natural way, for the statistical variability of lifetime data. The model as applied to the Crane data indicates that when the effects of temperature and depth of discharge are taken into account, the observed variability in lifetime data is due almost entirely to statistical variability inherent in the battery itself.

Molecular deformation and stress‐strain behavior of poly(bisphenol‐A‐diphenyl sulfone)

Stress‐optical studies have been carried out to determine the modes of molecular deformation in poly(bisphenol‐A‐diphenyl sulfone) and its relationship to stress‐strain behavior. Stress and birefringence were measured simultaneously as a function of strain at a strain rate of 0.0133 min−1 in the temperature range −179 to 150 °C. In the temperature range from 150 to −100 °C, measurements were performed using four strain rates, 0.0133 min−1, 0.133, 1.33, and 13.3 min−1 at each testing temperature. The results indicate that the processes involved in the molecular deformation appear to be invariant at temperatures below −100 °C. At higher temperatures, the statistical chain segments participate in the deformation process and the degree of participation increases with increasing temperature. The mechanism controlling the stress‐strain response is attributed to chain orientation. The stress‐strain response at temperatures below −100 °C is attributed to the temperature dependence of an internal energy contributi...