*2.2. Models Design*

Single-edge-notched bend (SENB) specimens were used in this study, and four different basic models were designed, which contain the "121" model, "123" model, "12321" model and "12324" model, as shown in Figure 3.

**Figure 3.** *Cont*.

**Figure 3.** Four different basic models, (**a**) "121" model, (**b**) "123" model, (**c**) "12321" model and (**d**) "12324" model.

These models are similar to sandwiches. The "121" model means the model contains "1" and "2" two kinds of materials, the materials in the model from left to right are "1", "2" and "1". The "123" model means the model contains "1", "2" and "3" three kinds of materials, the materials in the model from left to right are "1", "2" and "3". The "12321" model means the model contains "1", "2" and "3" three kinds of materials, the materials in the model from left to right are "1", "2", "3", "2" and "1". The "12324" model means the model contains "1", "2", "3" and "4" four kinds of materials, the materials in the model from left to right are "1", "2", "3", "2" and "4". Furthermore, the "121" model represents the single metallic welded joint, the "123" model represents the bimetallic welded joint, the "12321" and "12324" models represent the dissimilar metal welded joint.

For all the models, a load roll is applied at the top and center of the SENB specimen, and two back-up rolls are applied at the bottom of the SENB specimen. The loading is applied at the load roll by prescribing a displacement of 6 mm, and the two back-up rolls are fixed by control displacement and rotation. The initial crack is located in the middle of specimen. All the specimen widths are 14.4 mm (*W* = 14.4 mm), the loading spans are 57.6 mm (*L* = 4*W*), the specimen thicknesses *B* are 12 mm, and the initial crack lengths are 7.2 mm (*a/W* = 0.5).

Different material constraints were obtained by changing the width (the direction perpendicular to the initial crack) of 52Mb or 52Mw in each model. For the "121" and "123" models, changing the width of 52Mb from 0 to 80 mm. When the width of 52Mb is 0 mm, the welded joint is the same as the A508 and 316L homogeneous material models, respectively; when the width of 52Mb is 80 mm, the welded joint is same as the 52Mb homogeneous material model. For the "12321" and "12324" models, the widths change to 52Mb and 52Mw, respectively. When changing the width of 52Mb individually, the width of 52Mw is fixed to 1 mm, and changing the width of 52Mb from 0 to 80 mm; when changing the width of 52Mw individually, the width of 52Mb is fixed to 1 mm, and changing the width of 52Mw from 0–39.5 mm.
