PSI - Issue 68

5

D. Tomerlin et al./ Structural Integrity Procedia 00 (2025) 000–000

D. Tomerlin et al. / Procedia Structural Integrity 68 (2025) 1237–1244

1241

3. Results and discussion 3.1. Fracture toughness results

After the SENB specimens three-point bending testing, the maximum applied load P vs. Crack Mouth Opening Displacement (CMOD) results are obtained (Table 2). The specimens marked with * exhibited pop-in unstable brittle behavior. Testing of those specimens according to ASTM E1820 is not relevant, therefore ASTM E399 (2022) standard for linear-elastic plane-strain fracture toughness is used. Fig. 4 shows the P -CMOD curves, representative of simulated HAZ microstructures. It is visible that constrained specimens exhibit less resistance, with lower external loads P , as compared with the unconstrained specimens. Such behavior can be related to the residual stress levels, which are higher in constrained specimens. According to ASTM E1820, the material fracture resistance is determined using J - R curves (Fig. 5) and Crack Tip Opening Displacement CTOD( δ )- R curves (Fig. 6). The fracture testing characteristic values J IC , K JIC , and δ IC are also determined (Table 2).

Table 2. ASTM E1820 fracture toughness parameters Specimen P max [kN]

2 ]

1/2 ]

CMOD max [mm]

J IC [kJ/m

JIC [MPa∙m

IC [mm]

K

δ

microstructure

1.1

12.20

0.96 1.76 0.86 0.46 1.24 1.46 0.99 0.78 1.13

68.60

120.31 46.94 93.01 38.45 85.17 92.72 48.11 98.55 101.44

0.046

-

2.3*

9.18 9.23 7.19 9.66 7.89 8.60 6.90 9.87

-

-

A (SC CGHAZ) B (IC CGHAZ)

3.2

48.30

0.038

4.2*

-

-

C (FGHAZ) D (CGHAZ)

5.2

45.90 30.70 37.25

0.028 0.024 0.025

2.2C 3.2C

A (SC CGHAZ) B (IC CGHAZ)

4.2C*

-

-

C (FGHAZ) D (CGHAZ)

5.2C

42.90

0.028

Fig. 4. P -CMOD curves for simulated HAZ microstructures