Issue 75

V. Thondamon et alii, Fracture and Structural Integrity, 75 (2026) 88-103; DOI: 10.3221/IGF-ESIS.75.08

fracture toughness are 0.736, 0.619 and 0.810 respectively. The fracture ratios evaluated using J-integral by load-CMOD method are 0.694, 0.588 and 0.787 respectively. Fig. 7 shows the FAD using limit load moment proposed by Zahoor and fracture resistance in terms of initiation fracture toughness. Fig. 8 shows the FAD using limit load moment proposed by Zahoor [14] and fracture resistance in terms of J integral using load-CMOD method. Fig. 9 shows the FAD using limit load moment proposed by Takahashi and fracture resistance in terms of initiation fracture toughness. Fig. 10 shows the FAD using limit load moment proposed by Takahashi [15] and fracture resistance in terms of J-integral using load-CMOD method.

Load ratio, Lr

Fracture ratio, Kr

Initiation fracture toughness method

Load-CMOD method

Specimen No.

Zahoor [14]

Takahashi [15]

SP6-60-TWC-SSW-M1

0.572 0.494 0.462

0.778 0.672 0.628

0.736 0.619 0.810

0.694 0.588 0.787

SSPW 6-25 SSPW 12-27

Table 2: Load and fracture ratios for the welded pipe specimens.

For SP6-60-TWC-SSW-M1, the load ratio using expression proposed by Takahashi is 0.778 and the fracture ratio using initiation fracture toughness method is 0.736. For SSPW 6-25, the load ratio using expression proposed by Takahashi is 0.672 and the fracture ratio using initiation fracture toughness method is 0.619. For SSPW 12-27, the load ratio using expression proposed by Takahashi is 0.628 and the fracture ratio using initiation fracture toughness method is 0.810. From Fig. 8, it can be observed that the assessment point for SSPW 6-25 lies within the failure assessment line and the assessment point for SSPW 12-27 and SP6-60-TWC-SSW-M1 lies marginally inside the failure assessment line. Therefore, specimen SSPW 6-25 is considered to be safe and the specimens SSPW 12-27 and SP6-60-TWC-SSW-M1 is considered to be critical. Similar assessment has been carried out for all the specimens using expressions proposed by Zahoor and Takahashi for evaluating load ratio. The initiation fracture toughness and J-integral using load-CMOD method were used for evaluating fracture ratio. All the specimens lie within the stable region for all the assessments. For limit load moment proposed by Takahashi, specimens SSPW 12-27 and SP6-60-TWC-SSW-M1, is closer to the failure assessment line indicating that for the given notch length and applied load, the specimens are in a critical condition.

1.5

SP6-60-TWC-SSW-M1 SSPW 6-25 SSPW 12-27 SINTAP

Unstable

Critical

1.0

BS 7910 2A BS 7910 2B

0.5

Stable

Fracture ratio, Kr

L r

L r

max

max

0.0

0.0

0.5

1.0

1.5

Load ratio, Lr

Figure 7: FAD using limit load moment by Zahoor and initiation fracture toughness.

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