Structural Health Monitoring and Damage Prognosis in Fatigue

A conceptual structural health monitoring (SHM) system to monitor fatigue damage is discussed in this study. The first part of the study is concerned with damage prognosis. A methodology to use the data from a pre-crack damage monitoring system to predict the number of cycles to macrocrack-initiation in a probabilistic sense, is presented. Issues related to quantifying damage, a damage evolution law, and numerical evaluation of the probability of macrocrack initiation are discussed. The second part of the study deals with quantifying the effects of imperfect inspections during the growth of a macrocrack. The probability that there eXists an undetected critical crack is the quantity of interest. An analytical eXpression for this quantity is derived for the case of a two-dimensional crack. A Monte Carlo simulation method to quantify the effects of imperfect inspections is also presented. Numerical results are presented for two eXamples of surface-breaking cracks with different geometries.