No abstract

To evaluate the integrity of a structure is to prove its ability to perform its mechanical functions for all modes of loading, normal or accidental, and throughout its life. In the context of the nuclear safety, for the most important structures such as the tank or the primary circuit, the presence of a degradation in these structures grouping several aspects, such as cracks created during welding. We seek then, to show the mechanical resistance for this defect mode. It also seeks to fit the mechanical resistance of a structure in the presence of a crack when the defects have been detected during an inspection. In this context, the fracture mechanics provides the necessary tools to analyze cracked components. Its purpose is to establish a fracture criterion to foreordain the loading margins in normal or accidental operating conditions. Each type of rupture must be the subject of a specific characterization.

Welding is used to realize permanent assembly in mechanical structures to assure the continuity of the parts to be assembled contrary to the other assembly techniques which have physical or chemical discontinuities. Generally, crack evolution depends on several intrinsic and extrinsic parameters of material. The aim of this work is to analyse the severity of crack defects on the mechanical behaviour of Welded joints. The cracks are considered located in the weld metal. The J-integral method was used to analyse the fracture behaviour of these structures by the two-dimensional finite element method using Cast3M code. The effect of the mechanical properties, the mismatching and the crack size on the J-integral values was highlighted. A good correlation between the FEM simulations and the literature analysis results was observed. We note that the loading mode affects directly the J-integral value and consequently on the mechanical behaviour of the weldment.