Issue 30

P. Corigliano et alii, Frattura ed Integrità Strutturale, 30 (2014) 304-310; DOI: 10.3221/IGF-ESIS.30.37 306 Four groups of hardness were used to define different σ-ε curves. In particular HV=140-160 was found to be coherent with respect to the experimental σ-ε curves previously performed on specimens, made of the same steel, and it was used for the assessment of the base material properties; values of HV=190, 230 and 270 were used for the heat affected zones and welded zones. HV values were first converted in HB hardness, then static tensile properties were calculated and reported in Tab. 1. Finally the true σ-ε curves were evaluated. The elastic strains (for  y ) were simply calculated as  /E; while the elastic-plastic strains (for  y ) were taken from the Ramberg-Osgood equation and the parameters were calibrated using the experimental σ-ε curve of the base material, keeping the horizontal Lüder’s plateau. Fig. 6 shows the material curves, obtained by hardness measurements and by tensile test carried out on a specimen made of the same steel. The hardest fillet weld could be the last one which was made during the welding process because the heat input may affect the hardness of the previously welded ones. Figure 3 : Different material zones. Figure 4 : Hardness measurements. Figure 5 : Hardness values. HV  y [MPa]  u [MPa] E [MPa] 140 300 460 205000 190 421 636 230 542 780 270 656 908 Table 1 : Hardness measurements and related mechanical properties. Figure 6 : True stress-strain curve depending on hardness measurements.