3 RELIABILITY METHODS FOR FATIGUE-CRACK GROWTH

In this paper, three reliability methods (1) a first order reliability method (FORM) based on the total derivative method (TDM), (2) FORM ba sed on the Lagrange multiplier formulation (LMF) and (3) a Monte Carlo Simulation (MCS) with pseudo-exact sampling technique are applied to curvilinear fatigue crack growth problems. The crack can follow an arb itrary path which is determined by a crack direction law. A boundary i ntegral element method is used to determine the mechanical response. W ith the help of the pseudo-exact sampling technique used in MCS, we ar e able to determine an extremely low probability of failure as low as 10(-6) with high accuracy. A comparison of the three methods shows tha t the LMF is the most efficient method for the general fatigue crack g rowth reliability problems. For the class of problems we considered, L MF agrees very well with Monte Carlo simulation, indicating that it is quite accurate.