Issue 69

D. Leonetti et alii, Frattura ed Integrità Strutturale, 69 (2024) 142-153; DOI: 10.3221/IGF-ESIS.69.11

1250

1000

750

R350HT L1 R350HT L2 R350HT R1 R350HT R2

500

250 Stress [MPa]

0

0

2.5

5

7.5 10 12.5

Strain [%]

Figure 1: Monotonic engineering stress-strain curves, [15].

E [GPa]

σ 0.2,p [MPa]

UTS [MPa]

219 ± 3.2 1232 ± 3.8 Mean ± standard error, calculated as the ratio between the estimator of the standard deviation and the square root of the sample size. Table 2: Average tensile properties. 839 ± 4.2

Precracking

Fracture Toughness Test

Specimen

Pmax [kN]

a [mm]

P Qsi [kN]

P max [kN]

K Isi [MPa mm

0.5 ]

01 02 03

8.60 8.60 8.60

19.3 20.2 20.0

17.1 15.8 15.4

20.6 18.7 19.3

1237 1221 1172

Average: 1210 ± 20 (a) (a) Mean ± standard error, calculated as the ratio between the estimator of the standard deviation and the square root of the sample size. Table 3: Results of the linear elastic plane strain fracture toughness tests.

Figure 2: Fractography of the fracture toughness specimen 02; (a) Fatigue pre-crack zone and locations of the observations on the half width of the specimen, (b) one of the crack initiations from the notch produced by Electric Discharge Machining, (c) Fatigue pre-crack growth surface, (d) Transition from fatigue pre-crack to the final fracture region, (e) Final fracture region.

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