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Interrupted fatigue testing with periodic tomography to monitor porosity defects in wire + arc additive manufactured Ti-6Al-4V

Biswal, Romali; Zhang, Xiang; Shamir, Muhammad; Mamun, Abdullah Al; Awd, Mustafa; Walther, Frank and Khadar Syed, Abdul (2019). Interrupted fatigue testing with periodic tomography to monitor porosity defects in wire + arc additive manufactured Ti-6Al-4V. Additive Manufacturing, 28 pp. 517–527.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1016/j.addma.2019.04.026
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Abstract

Porosity defects remain a challenge to the structural integrity of additive manufactured materials, particularly for parts under fatigue loading applications. Although the wire + arc additive manufactured Ti-6Al-4 V builds are typically fully dense, occurrences of isolated pores may not be completely avoided due to feedstock contamination. This study used contaminated wires to build the gauge section of fatigue specimens to purposely introduce spherical gas pores in the size range of 120–250 micrometres. Changes in the defect morphology were monitored via interrupted fatigue testing with periodic X-ray computed tomography (CT) scanning. Prior to specimen failure, the near surface pores grew by approximately a factor of 2 and tortuous fatigue cracks were initiated and propagated towards the nearest free surface. Elastic-plastic finite element analysis showed cyclic plastic deformation at the pore root as a result of stress concentration; consequently for an applied tension-tension cyclic stress (stress ratio 0.1), the local stress at the pore root became a tension-compression nature (local stress ratio −1.0). Fatigue life was predicted using the notch fatigue approach and validated with experimental test results.

Item Type: Journal Item
Copyright Holders: 2019 The Authors
ISSN: 2214-8604
Keywords: Additive manufacturing; Porosity defects; X-ray computed tomography; Finite element modelling; Fatigue life prediction; Titanium alloy
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Computing and Communications
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 61977
Depositing User: ORO Import
Date Deposited: 19 Jun 2019 08:42
Last Modified: 26 Jun 2019 17:13
URI: http://oro.open.ac.uk/id/eprint/61977
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