PSI - Issue 68

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 68 (2025) 610–618

European Conference on Fracture 2024 Cyclic-elastic behavior in plastically pre-strained lattice structures *Ivan Senegaglia a , *Giuseppe Macoretta a , Tommaso Grossi a , Bernardo Disma Monelli a a Department of Civil and Industrial Engineering, University of Pisa, Largo Lucio Lazzarino 2, Pisa 57123, Italy Abstract The study investigates the evolution of elastic behavior in lattice structures subjected to cyclical loading after pre-straining to various levels of plastic deformation. Triply Periodic Minimal Surface (TPMS) gyroid lattice specimens were fabricated using the Laser Powder Bed Fusion (L-PBF) technique and subjected to controlled steps of compressive pre-straining, inducing plastic deformations. Subsequently, the specimens underwent cyclic loading-unloading tests to characterize their elastic behavior. Stress strain curves were monitored throughout the testing to determine the apparent elastic modulus ( E* ) at each cycle. The results demonstrate that E* of pre-strained lattices are not static. The initial cycles after pre-straining exhibit a change in stiffness, with the E* initially increasing depending on the pre-strain level. This behavior is attributed to the morphology of the lattice itself, which is more sensible to local hardening due to an evident bending-dominated mechanical response. Over slight plastic strains, the elastic modulus stabilizes, reaching a new stiffening-to-plastic strain evolution. The magnitude of this shift and the experimental response’s dispersion are found to not be dependent on the pre-strain level. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Elasticity; Plasticity; Elastic modulus; TPMS; Gyroid; Additive Manufacturing; L-PBF. 1. Introduction Lattice structures, prized for their tunable mechanics and minimal energy geometrical distribution, are increasingly used in engineering applications (Beghini et al., (2024); Senegaglia et al., (2024); Soro et al., (2022)). One of the most intriguing applications of metallic lattice structures involves their potential for impact mitigation (Maskery et al., © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

* Corresponding author. Tel. +39 388 58 98 718 E-mail address: ivan.senegaglia@phd.unipi.it, giuseppe.macoretta@unipi.it

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.105