Failure probability calculation of an axisymmetrically cracked pip under pressure and tension using a finite element code

摘要

Reliability analyses of structural components aim at estimating the probability that the external loading exceeds the structures resistance. In some industrial cases, the failure of the structure cannot be defined by an explicit function of therandom variables and only an implicit definition of the limit state function is available. It is the case when finite element calculations are used. Therefore, combining reliability codes with finite element codes is very important for the development ofreliability methods.This paper deals with the calculation of the failure probability of an axisymmetrically cracked pipe under pressure and tension using a finite element code with incremental non linear plasticity. The failure criteria corresponds to the crack initiationthat is to say when the Rice's integral reaches the material fracture toughness. Five random variables are considered: the material fracture toughness and the coefficients of the Ramberg-Osgood law (the Young's modulus, the yield strength, the strainhardening exponent and the Ramberg-Osgood coefficientα). The pipe reliability is evaluated as a function of the applied tensile stress using different combining methods and different reliability and finite element codes: a direct combining between theLaRAMA code RYFES and ANSYS; a surface response method between PROBAN and Code-Aster or COMREL and ANSYS.The results obtained using those two different combining methods with those different tools are similar for all the considered applied tensile stresses which correspond to very different reliability levels.