ON THE RELIABILITY OF DANIELS SYSTEMS

The available theoretical results on time-invariant and time-variant Daniels systems with emphasis on asymptotic solutions are first reviewed. It is found that the methodology for static Daniels systems is well developed. Further research is necessary for time-variant Daniels systems where the model for the failure process includes multiple componental failure, strength deterioration caused by load-induced fatigue and the dynamics of load effect redistribution. From numerical studies for small systems some conclusions concerning the extra reliability due to redundancy in general systems are then drawn. Significant extra reliability in small systems is, in fact, only available if the components are weakly dependent, have somewhat ductile stress-strain behavior and if the load variability does not exceed substantially the variability of strength. © 1990.