Modelling of ductile crack growth in welded joints using micromechanical failure criterion

Abstract

In this paper, ductile crack growth in strength mismatched welded joints is considered. High-strength low-alloyed (HSLA) steel in quenched and tempered condition is used as the base metal. Two different fillers are selected to obtain over- and undermatched weld metal. The fluxcored arc-welding process in shielding gas is applied. Constraint effect is tested by varying widths of the welded joints - three different weld metal widths are used: 6, 12 and 18 mm. Single-edged notched bend specimens (SENB) are experimentally and numerically analysed. Fatigue pre-crack is located in weld metal for all tested specimens (a0/W = 0.32). Ductile crack growth initiation and stable crack growth are modelled using the coupled micromechanical model proposed by Gurson, Tvergaard and Needleman (GTN model). A comparison of force F vs. crack tip opening displacement (CTOD) curves during crack growth is given as determined both experimentally and numerically using the GTN model for the later. Failure criterion used in numerical analysis is discussed in detail.