PSI - Issue 13

Rui Guo et al. / Procedia Structural Integrity 13 (2018) 2202–2209 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Figure 9 Equivalent plastic strain distributions at the tip of the three different length cracks at the sampling position (a)a=4mm (b)a=5mm (c)a=6mm

In order to observe the crack tip plastic strain caused by the axial welding residual stress, the Y-direction tensile plastic strain of the three different length crack tips at the sampling position was studied, as shown in Fig. 10. As shown in Fig. 10(a), a obvious strain boundary line appears near the crack tip, indicating that the Y-direction tensile plastic strain distribution varies in different materials. The strain distribution on both sides of the crack is uneven, and the stress distribution on the side close to the welding interface is smaller. As shown in Fig. 10(c), it can be seen that there is a strain boundary line in the contour map, the strain distribution is asymmetric, and the stress distribution on the alloy side near the welding material 182 is larger. As shown in Fig. 10(b), when the crack is on the welding interface, the Y direction tensile plastic strain in the A533B side is smaller, and the side of the 182 alloy is larger. As shown in Table 1, the strength of the welding material 182 is smaller than that of the base metal A533B, indicating a small Y direction tensile plastic strain distribution exists in higher strength metal. Comparing Figures 9(a)(c) and 10(a)(c), it can be seen that when the crack tip is in the metal of less strength and close to the welding interface, the equivalent plastic strain and the Y-direction tensile plastic strain are relatively smaller; when the crack tip is in the metal of more strength and close to the welding interface, the plastic strains are larger near the welding interface. Comparing Fig. 10(a)(b)(c), the high Y direction tensile plastic strain region around crack tip increases with the crack length grows.

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Figure 10 Y direction tensile plastic strain distributions at the tips of the three different length cracks at the sampling position (a)a=4mm (b)a=5mm (c)a=6mm

5. Conclusions (1) The interface of the materials in the welded structure has an influence on the stress and strain distributions at the tip of the nearby cracks. The greater the discrepancy in the strength of the materials on both sides of the interface, the more obvious the difference in stress and strain distributions; (2) Under the same residual stress, the tensile stress in the crack tip region is larger and the plastic strain is smaller in the material with higher strength; (3) Due to the uneven material properties, even if the plastic strains of different materials on the two sides of the material interface are different in the same residual stress field, the crack near the material welding interface will