PSI - Issue 2_A

Yusuke Seko et al. / Procedia Structural Integrity 2 (2016) 1708–1715 Author name / Structural Integrity Procedia 00 (2016) 000–000

1712

5

1000 1200 1400 1600 1800 2000

1000 1200 1400 1600 1800 2000

(a) 2a=6mm, 2c=40mm

(b) 2a=9mm, 2c=40mm

at CTOD = 0.05mm

at CTOD = 0.05mm

0 200 400 600 800 Opening stress,  x (MPa)

0 200 400 600 800 Opening stress,  x (MPa)

h=2mm (TOP) h=2mm (BOT) h=6mm (TOP) h=6mm (BOT) h=8mm (TOP) h=8mm (BOT)

h=2mm (TOP) h=2mm (BOT) h=6mm (TOP) h=6mm (BOT) h=9.5mm (TOP) h=9.5mm (BOT)

x

x

y

y

Crack tip

Crack tip

( ) : Calculation point for opening stress

( ) : Calculation point for opening stress

0 0.2 0.4 0.6 0.8 1 Distance from crack tip, y (mm)

0 0.2 0.4 0.6 0.8 1 Distance from crack tip, y (mm)

Figure 4 Crack opening stress distribution near crack tip at CTOD = 0.05 mm

2000

2000

(b) 2a=9mm, 2c=40mm m=20

(a) 2a=6mm, 2c=40mm m=20

1800

1800

1000 Weibull stress,  w (MPa) 1200 1400 1600

1000 Weibull stress,  w (MPa) 1200 1400 1600

h=2mm h=6mm h=9.5mm

h=2mm h=6mm h=8mm

0 0.1 0.2 0.3 0.4 0.5 0.6

0 0.1 0.2 0.3 0.4 0.5 0.6

Overall strain,  ∞ (%)

Overall strain,  ∞ (%)

Figure 5 Effect of crack depth on relationship between Weibull stress and overall strain

4. The effect of welding residual stress on Weibull stress of embedded flaw Welding residual stress has a large effect on the brittle fracture limit of a welded joint. Yamashita and author presented the welding residual stress decrease the brittle fracture limit of a welded joint with a through notch and surface notch based on the Weibull stress criterion. However, in the case of embedded crack, the Weibull stress of embedded crack would not increase due to compressive welding residual stress around the center of thickness. Therefore, the effect of welding residual stress on the Weibull stress of embedded crack was investigated by finite element analysis. 4.1. Finite element analytical model Half model of Center embedded crack panel with 25 mm thickness, 200 mm width and 200 mm length was modeled because of symmetry. Crack length, 2c, was set to 40 mm, Crack depths, h, were set to 2, 9.5 mm in the case of crack height 2a = 6 mm, and 2, 8 mm in the case of 2a = 9 mm. Other conditions regarding to modeling was same as chapter 3. ABAQUS standard ver. 6.13.3 was used for FE-analysis. The welding residual stress of K-groove welded joint made by 780 MPa class steel was introduced to analytical model. Introduced welding residual stress distribution was