Issue 78

T. Nasri et alii, Frattura ed Integrità Strutturale, 78 (2026) 275-297; DOI: 10.3221/IGF-ESIS.78.17

In this context, the present work proposes an enriched Paris law formulation based on first-kind Chebyshev polynomials to explicitly incorporate crack–microstructure interactions into crack propagation kinetics. The normalized variable ξ = ሺ a d ሻ ⁄ ∈ [ − 1, 1] relates the crack position to the grain size. The enriched law , d /dN = C·( Δ K) ⁿ · μ ( ξ ), preserves the classical Paris structure while introducing a local modulation capable of reproducing propagation oscillations at grain boundaries. The model is applied to two orientations of holed AA2024-T351 specimens. The remainder of the paper presents the material and experimental procedure, the mathematical formulation, the parameter identification strategy, and the corresponding results and physical interpretation.

M ATERIAL AND EXPERIMENTAL PROCEDURE

T

his section presents the investigated material, its microstructural characterisation, and the experimental procedure followed to obtain the fatigue crack propagation data used throughout this study. Material: AA2024-T351 The material investigated is the AA2024-T351 aluminium alloy (Al–Cu–Mg series, EN 573-3 standard), supplied as a 30 mm thick rolled plate. This alloy is widely used in primary aircraft structures - fuselage skins, wing panels, frames - due to its high specific strength, good ductility and fatigue resistance. The nominal chemical composition and monotonic mechanical properties are given in Tabs. 1 and 2, respectively.

Cu

Mg

Mn

Fe

Si

Zn

Ti

Al

3.8–4.9

1.2–1.8

0.3–0.9

≤ 0.50

≤ 0.50

≤ 0.25

≤ 0.15

Bal.

Table 1: Nominal chemical composition of AA2024-T351 (wt.%, EN 573-3).

Property

E (GPa)

Rp0.2 (MPa)

Rm (MPa)

A% (fracture)

Typical value (L direction)

73

325

470

≥ 15

Table 2: Monotonic mechanical properties of AA2024-T351.

Figure 1: EBSD characterisation of AA2024-T351 - TL direction. (a) Grain orientation map. (b) Recrystallisation map. (c) Pole figures {111} and {100}.

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