Papers by Keyword: Mismatched Welded Joint

Abstract: Stress corrosion cracking (SCC) is one of the key issues of welded structure failure in nuclear power plants. To understand the effect of strength matching on SCC growth rate in welded joint of primary coolant circuit safe end in pressured water reactor, a model of the safe end welded joint with mismatched strength was established by using elastic-plastic finite element method (EPFEM).The effect of weld strength matching on SCC growth rate was analyzed in this paper, by adopting crack tip strain rate as SCC mechanical driving force. The investigated results indicate that the distribution of plastic strain and plastic strain rate nearby the crack front is similar when the crack located at welded metal, and the driving force of SCC along the crack front in the over-match, even-match and under-match welded joint are from small to large, respectively, which implicit SCC growth rate along the crack front in the over-match, even-match and under-match welded joint also are from slow to fast, respectively. The investigating establishes a foundation for improving the predicting capability of SCC growth rate in nuclear power structures.

Abstract: Effect of weld metal hardening property on the deformation behavior and crack driving force of strength mismatched welded joint with crack has been investigated using finite element method under plain strain condition. The results show that when the apply load is small, there is only small scale deformation around the crack tip, the whole structure is still in linear or small scale yielding condition therefore the weld metal hardening property has no significant effect on crack driving force. As the applied load increasing, the deformation region enlarges and at the same time the deformation level around the crack tip deepens, the increasing of weld metal hardening property decreases the local deformation level, consequently leading to the decreasing of the crack cracking force.

Abstract: In this paper the micromechanical approach to ductile fracture was applied in a study of constraint effect on crack growth initiation in mismatched welded joints. The single-edged notched bend specimens (precrack length a0/W=0.32) were experimentally and numerically analyzed. The coupled micromechanical model proposed by Gurson, Tvergaard and Needleman was used. Constraint effect was tested by varying widths of the welded joints (6, 12 and 18mm). Highstrength low-alloyed (HSLA) steel was used as the base metal in a quenched and tempered condition. The flux-cored arc-welding process in shielding gas was used. Two different fillers were selected to obtain over- and undermatched weld metal. The micromechanical parameters used in prediction of the crack growth initiation on precracked specimen were calibrated on a round smooth specimen. The difference in fracture behavior between over- and undermatched welded joints obtained in experimental results was followed by numerical computations of void volume fraction in front of the crack tip.