CURVILINEAR FATIGUE-CRACK RELIABILITY-ANALYSIS BY STOCHASTIC BOUNDARY-ELEMENT METHOD

In this paper, the stochastic boundary element method, which combines the mixed boundary integral equations method explored in Reference 1 w ith the first-order reliability method, is developed to study probabil istic fatigue crack growth. Due to the high degree of complexity and n on-linearity of the response, direct differentiation coupled with the response-surface method is employed to determine the response gradient . Three random processes, the mode I and mode II stress intensity fact ors and the crack direction angle, are included in the expression of t he response gradient. The sensitivity of these random processes is det ermined using a first-order response model. An iteration scheme based on the HL-RF method2 is applied to locate the most probable failure po int on the limit-state surface. The accuracy and efficiency of the sto chastic boundary element method are evaluated by comparing the cumulat ive distribution function of the fatigue life obtained with Monte Carl o simulation. The reliability index and the corresponding probability of failure are calculated for a fatigue crack growth problem with rand omness in the crack geometry, defect geometry, fatigue parameters and external loads. The response sensitivity of each primary random variab le at the design point is determined to show its role in the fatigue f ailure. The variation of each primary random variable at the design po int with the change of probability of failure is also presented in num erical examples.