Reliability analysis and inspection updating by stochastic response surface of fatigue cracks in mixed mode

The analysis of engineering structures under fatigue crack growth aims at ensuring an appropriate reliability level over the entire operational lifetime. This paper deals with a new approach, namely the Stochastic Response Surface, to couple finite element analysis and reliability methods. The stochastic collocation method provides an explicit expression of the limit state function related to fatigue failure. This expression is used in first and second order reliability methods in order to compute the failure probability at a given structural age. When inspection is carried out, the structural reliability can be easily updated in terms of the observed crack length. Two numerical applications dealing with fatigue crack growth are presented to illustrate the proposed method, showing its performance in terms of numerical efficiency and accuracy

Toward Optimal Updating Time Inspection Based on Reliability Approach of Fatigue Crack Propagation

It is well-established that fatigue crack growth process is one of the main process which can produce failure of structures and mechanical components. The aim of this work is to develop a model predicting an updating inspection time model for structural fatigue crack growth life based on updating reliability analysis taking into account the additional information generated by the previous inspection results. First order reliability method (FORM) and Surface response method are used to evaluate the reliability. The uncertainties such as material parameters and geometrical parameters which affect the lifespan of the structure were regarded as random variables. Updating reliability assessment based on Bayesian approach was introduced to determine the updating inspection time for target reliability. The method was illustrated through an application to a plate with an emergent rectilinear crack loaded with a constant amplitude cyclic stress. The results of the application are in a good agreement with the physical results and show that the proposed method is proved to be feasible and applicable in the general complex fatigue loading and able to give accurate updating framework for scheduling inspections. Furthermore the proposed approach leads to determine the optimal Inspection time strategy based upon cost-minimization by considering a single type or multiple types of inspections