Fatigue Reliability of Parallel Systems

Abstract

An exact general closed‐form approach to estimation of fatigue reliability of parallel systems, which represent a set of failure paths of structural systems, is presented. The parallel system considered here is completely general and comprises components that are of different strength and share unequal loads. The system failure is regarded as the sequential failure of its members. A general expression for the notional probability of fatigue failure of this system is developed using Wirsching's model of fatigue failure of the system nodes and by relating the compressed times to failure of nonfailed nodes following failure of some of the nodes in the system to their nominal times to failure corresponding to the state when all system members are intact. The general expression is first validated by comparison to a known parallel system in which system members are of equal strength and share equal loads, and then employed to estimate the failure probability of another system in which the system components are of unequal strength.