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

Romali Biswal, Xiang Zhang, Muhammad Shamir, Abdullah Mamun, Mustafa Awd, Frank Walther, Abdul Syed

Research output: Contribution to journalArticle

34 Downloads (Pure)

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.

Original languageEnglish
Pages (from-to)517-527
Number of pages11
JournalAdditive Manufacturing
Volume28
Early online date1 May 2019
DOIs
Publication statusPublished - Aug 2019

Fingerprint

Fatigue testing
Tomography
Porosity
Fatigue of materials
Wire
Defects
Structural integrity
Feedstocks
Gages
Stress concentration
Plastic deformation
Compaction
Contamination
Gases
Plastics
Scanning
Finite element method
X rays

Bibliographical note

Open access under a Creative Commons license

Funder

EPSRC

Keywords

  • Additive manufacturing
  • Fatigue life prediction
  • Finite element modelling
  • Porosity defects
  • Titanium alloy
  • X-ray computed tomography

ASJC Scopus subject areas

  • Biomedical Engineering
  • Materials Science(all)
  • Engineering (miscellaneous)
  • Industrial and Manufacturing Engineering

Cite this

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; Awd, Mustafa; Walther, Frank; Syed, Abdul.

In: Additive Manufacturing, Vol. 28, 08.2019, p. 517-527.

Research output: Contribution to journalArticle

@article{df64bc367c984bef82e92abd2003d63e,
title = "Interrupted fatigue testing with periodic tomography to monitor porosity defects in wire + arc additive manufactured Ti-6Al-4V",
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.",
keywords = "Additive manufacturing, Fatigue life prediction, Finite element modelling, Porosity defects, Titanium alloy, X-ray computed tomography",
author = "Romali Biswal and Xiang Zhang and Muhammad Shamir and Abdullah Mamun and Mustafa Awd and Frank Walther and Abdul Syed",
note = "Open access under a Creative Commons license",
year = "2019",
month = "8",
doi = "10.1016/j.addma.2019.04.026",
language = "English",
volume = "28",
pages = "517--527",
journal = "Additive Manufacturing",
issn = "2214-8604",
publisher = "Elsevier",

}

TY - JOUR

T1 - Interrupted fatigue testing with periodic tomography to monitor porosity defects in wire + arc additive manufactured Ti-6Al-4V

AU - Biswal, Romali

AU - Zhang, Xiang

AU - Shamir, Muhammad

AU - Mamun, Abdullah

AU - Awd, Mustafa

AU - Walther, Frank

AU - Syed, Abdul

N1 - Open access under a Creative Commons license

PY - 2019/8

Y1 - 2019/8

N2 - 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.

AB - 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.

KW - Additive manufacturing

KW - Fatigue life prediction

KW - Finite element modelling

KW - Porosity defects

KW - Titanium alloy

KW - X-ray computed tomography

UR - http://www.scopus.com/inward/record.url?scp=85066486002&partnerID=8YFLogxK

U2 - 10.1016/j.addma.2019.04.026

DO - 10.1016/j.addma.2019.04.026

M3 - Article

VL - 28

SP - 517

EP - 527

JO - Additive Manufacturing

JF - Additive Manufacturing

SN - 2214-8604

ER -