Issue 29

L. Zhao et alii, Frattura ed Integrità Strutturale, 29 (2014) 410-418; DOI: 10.3221/IGF-ESIS.29.36 412 Figure 2 : Geometry of the DMW joint sub-model. Figure 3 : Crack locations and depths in the sub-model. Material mechanical property of the DMW joint The stress-strain relationship beyond yielding is represented as Romberg-Osgood equation at the loading stage, and the relationship is linearly elastic at the unloading stage in this simulation. Romberg-Osgood equation is written as: 0 0 0                n (1) where: σ 0 is the yield strength of the material; ε 0 is the yield strain of the material;  is the dimensionless material constant; n is the strain-hardening exponent of the material. The mechanical properties of materials are given in Tab. 1. The strain-hardening exponent of these materials is obtained in the following equation [10]. 0 1 ln(1390 / )    n (2) where κ =0.163. The microstructure characterization of the fusion boundary region of an Alloy 182-A533B LAS dissimilar weld joint has showed that there is a narrow high hardness zone (HHZ) in the dilution zone of Alloy 182. Further, a sharp increase of the hardness was observed in the HHZ of Alloy 182 [11]. High yield stress is consistent with high hardness. Therefore, Alloy 182 buttering has higher yield stress than that of Alloy 182 weld because of the existence of HHZ.