Issue 78

A. Gallo et alii, Fracture and Structural Integrity, 78 (2026) 489-503; DOI: 10.3221/IGF-ESIS.78.28

a) b) Figure 3 : Finite element model and boundary conditions; a) front view and b) side view

Optimized with LM

Optimized with NLS

Optimized with MBS

Reference 1

Reference 2

41000

41000

41000

41000

41000

E [MPa]

0.35 221 316 0.43

0.35 221

0.35 221

0.35 221

0.35 221

ν [-]

A [MPa] B [MPa]

270.35 0.2155 0.0388

285.91 0.2757 0.0069

276.08 0.2607 0.0089

285.53 0.2753 0.0067

c [-] F [-]

0.5262

Table 1 : Identified JC parameters. The percentage difference between the objective function with respect to references 1 and 2 was η ଵ ൌ ி ೝ೐೑ , భି ி ೚೛೟ ி ೚೛೟ 100 ൌ 7683 % and η ଶ ൌ ி ೝ೐೑ , మି ி ೚೛೟ ி ೚೛೟ 100 ൌ 474 % , respectively. The values labelled “Reference 1” were evaluated after calibration in [23,24],whilst the term ሺ ሻ was correspondingly assessed using eq. (14). Similarly, the values indicated as “Reference 2” were estimated using the true stress– true strain curve, calculated from the experimental curve [23] by conserving volume as follows: ቊ ௧௥௨௘ ൌ ln ൫ 1 ൅ ௘௡௚ ൯ ௧௥௨௘ ≅ ௘௡௚ ൫ 1 ൅ ௘௡௚ ൯ Subsequently, from the true stress – plastic strain curves, obtained by curve fitting, the reference values were estimated as a starting point. The procedure carried out to obtain these starting values is shown as follows:

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