André T. Beck

Fatigue and fracture reliability analysis under random loading

Publisher Summary This chapter presents a paper that addresses the problem of fatigue-crack propagation and ultimate fracture of a structure or mechanical component under random loading. The problem is formulated by combining the first-passage failure model with stochastic models of crack propagation. The developed solution, based on the ensemble up-crossing rate approximation, requires a single mean crack growth computation, significantly speeds lifetime analysis, and allows consideration of nondestructive inspections. Many stochastic crack propagation models have been developed to represent and deal with the uncertainties involved in the problem. Most of these models consider failure as a dominating crack reaching a critical crack length. The resulting reliability models are time-invariant. Under random loading, the crack grows because ofbecause of stress reversals, reducing the resistance of the structure. Failure can occur at any timebecause of because of a peak of the random load process exceeding the instantaneous capacity of the structure. The problems of crack propagation and ultimate fracture cannot always be isolated, and more demanding time-variant reliability models are needed.