Stochastic Paris-Erdogan model for fatigue crack growth using two-state model

The one-state stochastic Paris-Erdogan crack model, da/dn = C(Delta K)(m) is extended and replaced by two-state model for fatigue crack growth. This is done by means of memoryless transformation and introduction of an auxilliary process. The mean and variance of the crack size are then derived analytically and the validity of the expressions obtained is verified by comparing them with simulation results. It is found that the results obtained from simulation and analytic expression are sufficiently in good agreement to allow us to conclude the validity of the analytic expression and to validate the numerical simulation procedure.