PSI - Issue 68

Emanuele Vincenzo Arcieri et al. / Procedia Structural Integrity 68 (2025) 1324–1328 E.V. Arcieri et al. / Structural Integrity Procedia 00 (2025) 000–000

1326

3

2. Description of the finite element model and influence of the impact speed on the damage The damage in an hourglass-shaped specimen caused by the normal impact of a ball was simulated using the Abaqus Explicit finite element code (2017). Both the hourglass specimen and the impacting ball were modelled as shown in Fig. 1 (Arcieri et al., 2021, 2022, 2023; Arcieri and Baragetti, 2024), with the first considered made of 7075-T6 aluminum alloy and the latter of steel. An aluminum alloy was chosen for the hourglass specimen, as impact damage is a major concern in aircraft engineering, and many aircraft components are made from lightweight alloys (Baragetti and Arcieri, 2023). Since the elastic modulus of the steel (E=210 GPa) is approximately three times the Young’s modulus of the aluminum (E=71.7 GPa), the ball was modelled as rigid. The material behavior of the specimen was assumed to be isotropic, homogeneous and elastic perfectly plastic, with a Poisson’s coefficient =0.3 and a yield stress YS=598 MPa (Arcieri et al., 2022). Strain hardening and temperature effects were therefore not considered in this preliminary model. The simulated impact occurred perpendicular to the outer surface of the specimen, at its minimum cross section. The mesh of the ball was made of linear quadrilateral rigid elements while the specimen was modelled with linear hexahedral elements. Friction contact was defined between the ball and the hourglass specimen, with a friction coefficient of 0.6 (Javadi and Tajdari, 2006). A portion of the lateral surfaces of the cylindrical parts of the hourglass specimen was fixed. The simulation for assessing the impact-induced damage was interrupted once the stresses in the impacted specimen could be considered constant over time. The damage resulting for impact speeds less than or equal to 240 m/s was investigated.

0 0,2 0,4 0,6 0,8 1 1,2 1,4

0 0,2 0,4 0,6 0,8 1 1,2 1,4

y = 9E-06x 2 + 0,003x R² = 0,9993

y = 1E-05x 2 + 0,0028x R² = 0,9997

dent depth (mm)

dent depth (mm)

0

100

200

300

0

100

200

300

impact speed (m/s)

impact speed (m/s)

(a)

(b)

(c) Fig. 2. Numerical results: (a) dent depth after impact for speed from 20 to 240 m/s and interpolation curve; (b) dent depth after impact for speed from 120 to 240 m/s and interpolation curve; (c) final displacement (mm) at the minimum cross section of the specimen for an impact case.