A Quality Assessment of Welded Joints of High Strength Steels in Relation to Brittle Fracture Initiation

Abstract

From critical COD δ_c of HT 80 welded bonds, brittle fracture initiation temperatures at the residual stress field are calculated using COD concept. These temperatures are compared with the temperature Ty, which is calculated from K_c using the equation K_c =√ Eσ _yδ_c· T_y indicates the temperature at which the brittle fracture initiation stress reaches to the yield stress of the material. It is clarified that the temperature T_y can be substituted approximately for the brittle fracture initiation temperature of welded joints with the residual stress of the longitudinally welded bead. The validity of T_y is certified by an example of cross-welded notch tests.
This paper proposes to employ this temperature T_y for the quality assessment of welded joints of high strength steels. T_y can be obtained from bending COD tests and tensile tests at low temperature.
An experimental example on HT 80 welded bonds shows a good correlation between T_yand Charpy transition temperature _v T_s, consequently giving the relation between the Charpy requirement and the defect size at HT 80 welded bonds.