Definition of a ‘materials’ database for heavy structures by experimental characterization of toughness-impact strength Original Research Article

With the prospect of a rapid and well-adapted application of the existing methods of predicting the fracture behaviour of welded assemblies in the presence of a defect, this study aims at gathering experimental data on the toughness of butt welded assemblies used in heavy sructures. This analysis of the toughness properties shows that the weld, and hence the various zones which compose it, have mechanical properties which are at least equal to those of the base metal. Although the E355 base metal contained niobium, the weld itself did not constitute a brittle zone in the welded assembly. Furthermore, the thickness of the welded plates seemed to have an effect on the mechanical behaviour of the HAZ only. For a thickness of 30 mm, this zone exhibits by far the highest toughness in the case of butt welded assemblies. Lastly, it is difficult to assess the beneficial or detrimental effect of the heat treatment applied for relieving the internal stresses because the metallurgical evolution in the weld, which takes place during the thermal cycle, sometimes embrittles or improves the toughness of the welded assembly. The application of the six models for predicting toughness as a function of temperature from the impact values of the base metal has shown that these correlations have a conservative range of validity. Outside the temperature-related range of validity, it was observed that Model (Rolf–Novak–Barsom), defined for the ‘end of ductile transition’ upper part was the most representative for predicting the toughness of the base metal as a function of temperature.