engleski

Fracture toughness comparison of mis-matched HSLA steel welds in three point SENB specimens

Mis-matched welded joints are joints in which the yield strength and or microstructures of the weld metal will be different from that of the base metal and HAZ. In the base metal, HAZ and weld metal combinations, the mis-match constraint is caused by both global mis-match and local mis-match. The global mis-match is defined as the ratio of the yield strength of weld metal to that of the base metal, whereas the local mis-match is defined as the ratio of the yield strength of the weld metal to that of the HAZ. Basically, overmatched welded joints influence larger part of the deformation to occur in the basic material, enabling a protective effect towards crack propagation in the weld metal or the HAZ. This paper contains determination of the fracture toughness, as well study and analysis of the effect of mis-match fracture behavior and crack growth in HSLA steel welded specimens with cracks in HAZ. The small overmatch of the welded joint has acted very protective in providing of good failure resistance. The barrier acting of the mis-match, after the initial propagation of the crack in FG HAZ or CG HAZ, has brought to change of its propagation direction through the more ductile base metal, thus decreasing the speed of propagation.

Fracture toughness; Mis-match ratio; Crack tip opening displacement; Stress concentration; Crack propagation

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