Crack analysis in main steam branch connections

Welded pipe connections in main steam line may contain defaults in the weld region. These flaws are modelized as cracks in order to analyse their stability. Their shapes and positions are strongly variable; parametric computations are then very useful. An other need is to look for the critical crack, i.e. the minimum length and the worst position of the crack which lead to instability. Simplified methods had been developed, in order to analyse easily and quickly cracks stability. These ones are based on stress intensity factors, determined from stresses values in branch connections without defaults. 3D finite element computations are then needed, for any loading, to provide stresses used in the analyse. These results are stored in a database. An user friend software, named MSPIQ, has been developed: it is based on these data. The user gives the cracks dimensions and positions, and MSPIQ provides elastic Stress Intensity Factors, Kj (with plastic correction) for any physical loading of the line. (authors). 4 refs., 2 figs