Predicting the Effect of Surface Waviness on Fatigue Life of a Wire + Arc Additive Manufactured Ti-6Al-4V Alloy

Muhammad Shamir, Xiang Zhang, Abdul Syed, Wayne Sadler

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
40 Downloads (Pure)


This paper reports the effect of as-deposited surface conditions on the fatigue strength of an additively manufactured titanium alloy, Ti-6Al-4V (WAAM Ti64). First, the local stress concentration caused by the surface waviness was quantified using a metrology technique and computer modelling. Fatigue tests were conducted under bending loads at a cyclic load ratio of 0.1. The applicability of two predictive methods was the focus of this study. The traditional notch stress method was unable to predict the correct S–N curve trend slope, which could be attributed to the early crack initiation from the troughs on the as-built surface, with crack propagation being the dominant failure mechanism. By treating the troughs as small cracks, the fracture mechanics approach delivered good predictions at every applied stress level. Surface machining and polishing may not always be practical or required; it depends on the applications and service load levels. This research demonstrated that the fracture mechanics approach can be used for predicting the fatigue life of WAAM titanium alloys in as-built conditions and, hence, can be a tool for decision making on the level of surface machining.
Original languageEnglish
Article number5355
Number of pages16
Issue number15
Publication statusPublished - 30 Jul 2023

Bibliographical note

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://


Engineering and Physical Science Research Council (EPSRC) through the NEWAM programme grant (EP/R027218/1)


  • WAAM
  • Surface waviness
  • Surface roughness
  • Fatigue
  • Bending test
  • Durability
  • Fracture mechanics


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