PSI - Issue 60

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

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ScienceDirect

Procedia Structural Integrity 60 (2024) 245–255

© 2024 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 the ICONS 2023 Organizers Aluminium 2024-T3 alloy, widely employed in transport aircraft wing and fuselage skin structures, necessitates thickness reduction for weight optimization. Chemical milling is utilized for this purpose; however, it removes Cladding (as a standard corrosion protection layer), prompting subsequent anodizing and sealing to provide corrosion protection. Literature indicates that anodizing or chemical milling can significantly reduce fatigue life, and limited data have been available on the life of chemically milled anodized materials. In this study, constant amplitude stress-life (S-N) testing was performed on two sets of fatigue samples: Cladded Aluminium Alloy (CAA) 2024-T3 sheet specimens (1.6 mm thick) and chemically milled, anodized and sealed (CMAS-AA) Aluminum Alloy sheet specimens (1 mm thick). S-N curves were generated at R=0.1 and room temperature under stress control. SEM micrographs showed micropores in CMAS-AA and a standard plain surface in CAA, consistent with prior findings. Both types exhibited 3-5 times shorter fatigue life than electropolished samples, as reported in MIL Handbook HDBK-5J, highlighting the importance of corrosion protection techniques for structural integrity. Residual stresses were observed, with cladded samples displaying compressive and CMAS-AA exhibiting tensile stresses. Fractography revealed no abnormal fatigue fracture features, and computed plane stress fracture toughness values estimated using measured crack size from the failed specimens matched standard values of aluminium alloys. © 2024 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) Third International Conference on Structural Integrity 2023 (ICONS 2023) Effect of chemical milling and anodizing on the high cycle fatigue behaviour of 2024-T3 aluminium alloy Chinnam Sivateja a , Naga Charan K V b , Ramesh Bojja a , Jagannathan N a , Manjunatha C M a, * a Structural Integrity Division, CSIR-National Aerospace Laboratories, Bengaluru-560017, Karnataka, India b Roddam Narasimha Civil Aircraft Center, CSIR-National Aerospace Laboratories, Bengaluru-560017, Karnataka, India Abstract

Peer-review under responsibility of the ICONS 2023 Organizers Keywords: Chemical milling; Cladding; Anodization; fatigue life; 2024-T3

* Corresponding author. Tel.: +91-080-25086300; fax: +91-080-25086310. E-mail address: manjucm@nal.res.in

2452-3216 © 2024 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 the ICONS 2023 Organizers

2452-3216 © 2024 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 the ICONS 2023 Organizers 10.1016/j.prostr.2024.05.046