The effect of the local hard zone (LHZ) distributed in the coarse grained HAZ (CGHAZ) has been analyzed by 2-dimensional FEM on a mechanical model of the weld CGHAZ. The existence of the LHZ elevates considerably the ...The effect of the local hard zone (LHZ) distributed in the coarse grained HAZ (CGHAZ) has been analyzed by 2-dimensional FEM on a mechanical model of the weld CGHAZ. The existence of the LHZ elevates considerably the stress in LHZ and causes the discontinuity of strain at the boundary between the LHZ and the matrix. The stress distribution in the LHZ is strongly affected by the shape of the LHZ. In a slender LHZ almost the whole region in the LHZ is exposed to elevated stress, whereas in the massive LHZ only the edge region sustains high stress. The longer the LHZ becomes, the more the highly stressed area, and the peak stress in the LHZ grows even under the same volume fraction of the LHZ. These results indicate that the slender LHZ brings about unstable fracture at a lower load level than the blocky LHZ. This tendency was confirmed by CTOD test results on the weld CGHAZ of a high-strength steel. The CGHAZ with elongated M-A constituents fractures at apparently lower critical CTOD than the CGHAZ with massive M-A constituents. In conclusion, the control of the shape of the M-A constituent has a striking effect on the toughness improvement of CGHAZ.展开更多
文摘The effect of the local hard zone (LHZ) distributed in the coarse grained HAZ (CGHAZ) has been analyzed by 2-dimensional FEM on a mechanical model of the weld CGHAZ. The existence of the LHZ elevates considerably the stress in LHZ and causes the discontinuity of strain at the boundary between the LHZ and the matrix. The stress distribution in the LHZ is strongly affected by the shape of the LHZ. In a slender LHZ almost the whole region in the LHZ is exposed to elevated stress, whereas in the massive LHZ only the edge region sustains high stress. The longer the LHZ becomes, the more the highly stressed area, and the peak stress in the LHZ grows even under the same volume fraction of the LHZ. These results indicate that the slender LHZ brings about unstable fracture at a lower load level than the blocky LHZ. This tendency was confirmed by CTOD test results on the weld CGHAZ of a high-strength steel. The CGHAZ with elongated M-A constituents fractures at apparently lower critical CTOD than the CGHAZ with massive M-A constituents. In conclusion, the control of the shape of the M-A constituent has a striking effect on the toughness improvement of CGHAZ.
