FRACTURE-MECHANICS EVALUATION OF CRACKED COMPONENTS WITH CONSIDERATION OF MULTIAXIALITY OF STRESS STATE

The fracture-mechanics evaluation of cracked components is an essentia l part of safety analyses. This evaluation is usually based on one-par ametric evaluation procedures without taking into account the multiaxi ality of the stress state. Considering the multiaxiality of the stress state across the flawed component cross-section, it is possible to re cognize and extend the limits of application of fracture mechanics, wh ich among others, are given by the limited transferability of fracture -mechanics material laws. Within the scope of the research project ''P henomenological Vessel Burst Tests-Phase IV'', T-branches and elbows w ith dimensions like the primary coolant lines of PWR plants were inves tigated. In addition to the experimental investigations, extensive num erical calculations were performed by means of the finite element meth od (FEM). To determine the stress and the gradient of multiaxiality ac ross the ligament of the component, 3-D finite-element analyses were c arried out concerning elastic-plastic material behaviour. The evaluati on with regard to crack initiation has been proven by experimental res ults as well as the qualitative assessment of the fracture behaviour o n the basis of the multiaxiality analyses.