PSI - Issue 39

Wei Song et al. / Procedia Structural Integrity 39 (2022) 204–213 Author name / Structural Integri y Procedia 00 (2020) 0 0–00

210

7

M=1

Weld toe

Weld root

M=1

150

150

120

120

90

90

2a/W=0.33

60

Kn

Kn

60

2a/W=0.267 2a/W=0.33

2a/W=0.267

30

2a/W=0.133 2a/W=0.2

2a/W=0.2

30

2a/W=0.133

0

0

1

1

Plastic energy values

Plastic energy values

0.8

0.8

0.6

0.6

0.4

0.4

1.4

1.4

1.2

1.2

0.2

0.2

1

1

0.8

0 0.6

0.8

0 0.6

weld length h/t

weld length h/t

(a) M=1 on weld root

(b) M=1 on weld toe

M=0.8

Weld root

M=0.8

Weld toe

600

600

500

500

400

400

300

300

2a/W=0.33

Kn

Kn

200

200

2a/W=0.267

2a/W=0.33 2a/W=0.267 2a/W=0.2

2a/W=0.2

100

100

2a/W=0.133

2a/W=0.133

0

0

1

1

Plastic energy values

Plastic energy values

0.8

0.8

0.6

0.6

0.4

1.4

0.4

1.2

1.4

0.2

1

1.2

0.2

0.8

0 0.6

1

0.8

0 0.6

weld length h/t

weld length h/t

(c) M=0.8 on weld root (d) M=0.8 on weld toe Fig. 4 NECF comparison of different mismatch ratios, penetration ratio and weld length.

The quantified transition relationships of the WR and WT failures under different geometries and yield strength configurations in LCWJs were explored, as shown in Fig. 5. Regarding the evenmatched CLWJs with fixed penetration length (2a/W=0.33) in Fig. 5(a), the fatigue failure transition curves between WT and WR locations for different penetration lengths and weld lengths were determined by intersection line of corresponding 3D contours. The evolution of the transition curves with the increases of penetration length (2a/W decreases) can be examined in Fig. 5(b), (c), and (d). It is seen that the longer penetration length leads to enhancing the load-carrying capacity of the LCWJ, and further makes the WT point the potential failure location. Note that the 3D contour of WT is entirely higher than that of WR location for 2a/W=0.133 (Fig. 5(d)) without any intersection point, which implies the final fatigue crack point occurred at the WT region. The fatigue failure transition curves with different penetration lengths and weld lengths for evenmatched LCWJs are drawn according to these intersection lines. On the other hand, the different configurations of geometries and mismatch ratios have a similar impact on the transition relationship of fatigue failure locations by deducing intersection lines based on the proposed analytical model. Hence, the transition relationship of fatigue failure location in the LCF regime can be predicted directly from the analytical equations.