The effect of manufacturing defects on the fatigue life of selective laser melted Ti-6Al-4V structures

Y.N. Hu; S.C. Wu; P.J. Withers; J. Zhang; H.Y.X. Bao; Y.N. Fu; G.Z. Kang

Materials & Design (Jul 2020)

The effect of manufacturing defects on the fatigue life of selective laser melted Ti-6Al-4V structures

Y.N. Hu,
S.C. Wu,
P.J. Withers,
J. Zhang,
H.Y.X. Bao,
Y.N. Fu,
G.Z. Kang

Affiliations

Y.N. Hu: State Key Lab. of Traction Power, Southwest Jiaotong University, Chengdu 610031, China
S.C. Wu: State Key Lab. of Traction Power, Southwest Jiaotong University, Chengdu 610031, China; Henry Royce Institute, Department of Materials, The University of Manchester, Manchester M13 9PL, UK; Corresponding author at: State Key Lab. of Traction Power, Southwest Jiaotong University, Chengdu 610031, China.
P.J. Withers: Henry Royce Institute, Department of Materials, The University of Manchester, Manchester M13 9PL, UK
J. Zhang: AVIC Manufacturing Technology Institute, Beijing 100024, China
H.Y.X. Bao: State Key Lab. of Traction Power, Southwest Jiaotong University, Chengdu 610031, China
Y.N. Fu: Shanghai Synchrotron Radiation Facility (SSRF), Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
G.Z. Kang: State Key Lab. of Traction Power, Southwest Jiaotong University, Chengdu 610031, China

Journal volume & issue: Vol. 192
p. 108708

Abstract

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The manufacturing defects introduced by selective laser melting typically lead to lower fatigue strength and a larger variation in fatigue life compared to conventionally manufactured structures. X-ray micro computed tomography (μCT) is used to characterize the porosity and lack of fusion defects in terms of population, morphology, dimension and location. The defect size and location are combined with the NASA/FLACGRO (NASGRO) fatigue crack growth model to predict the likely fatigue life, in which an effective initial crack length is defined using the cyclic plastic zone and the defect radius. An eXtended defect zone (XDZ) describing the propensity for local plasticity during fatigue around a defect has been shown through numerical analysis to be a good indicator of the ranking of the threat to fatigue caused by differently located manufacturing defects. This indicates that the effect of a defect, initial radius, r0, is likely to be pronounced when its center is within 2r0 of the surface and maximal when it lies just beneath the surface.

Published in Materials & Design

ISSN: 0264-1275 (Print); 1873-4197 (Online)
Publisher: Elsevier
Country of publisher: United Kingdom
LCC subjects: Technology: Electrical engineering. Electronics. Nuclear engineering: Materials of engineering and construction. Mechanics of materials
Website: https://www.journals.elsevier.com/materials-and-design

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