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Fatigue behaviour of additive manufactured Ti6Al4V, with as-built surfaces, exposed to variable amplitude loading
Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering. Saab AB, Aeronaut, SE-58188 Linkoping, Sweden.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering. Saab AB, Aeronaut, SE-58188 Linkoping, Sweden.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-8304-0221
2017 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 103, p. 353-362Article in journal (Refereed) Published
Abstract [en]

Additive Manufacturing (AM) allows for great design freedom compared to conventional manufacturing. This is very attractive for the aerospace industry in which AM could contribute to lightweight designs and thereby reduce fuel consumption, increase payload and extend flight range. The fatigue behaviour for rough as-built AM surfaces has previously been characterized with constant amplitude testing but in aerospace applications, most parts are exposed to variable amplitude loading. The fatigue behaviour for variable amplitude is not always consistent with the behaviour for constant amplitude due to effects of overloads and local plastic deformations. Therefore, variable amplitude loading behaviour of laser sintered and electron beam melted Ti6Al4V, with rough as-built surfaces have been investigated in this study using the Short-FALSTAFF (Fighter Aircraft Loading STAndard For Fatigue) load sequence. The predicted and the experimental fatigue life was overall consistent even though most experimental results exceeded the predicted life, especially for the laser sintered material. These findings show that conventional cumulative damage fatigue life predictions give reliable predictions for AM materials with rough as-built surfaces for the type of tension dominated load sequence used. (C) 2017 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD , 2017. Vol. 103, p. 353-362
Keywords [en]
Additive manufacturing; Ti6Al4V; Fatigue; Variable amplitude loading; Stress concentration
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:liu:diva-140783DOI: 10.1016/j.ijfatigue.2017.06.023ISI: 000407982800034OAI: oai:DiVA.org:liu-140783DiVA, id: diva2:1140994
Note

Funding Agencies|Saab AB; Swedish Foundation for Strategic Research; European Commission, through the Clean Sky 2 programme

Available from: 2017-09-13 Created: 2017-09-13 Last updated: 2017-11-15
In thesis
1. Fatigue Performance of Additive Manufactured Ti6Al4V in Aerospace Applications
Open this publication in new window or tab >>Fatigue Performance of Additive Manufactured Ti6Al4V in Aerospace Applications
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Additive Manufacturing (AM) for metals includes is a group of production methodst hat use a layer-by-layer approach to directly manufacture final parts. In recent years, the production rate and material quality of additive manufactured materials have improved rapidly which has gained increased interest from the industry to use AM not only for prototyping, but for serial production. AM offers a greater design freedom, compared to conventional production methods, which allows for parts with new innovative design. This is very attractive to the aerospace industry, in which parts could be designed to have reduced weight and improved performance contributing to reduced fuel consumption, increased payload and extended flight range. There are, however, challenges yet to solve before the potential of AM could be fully utilized in aerospace applications. One of the major challenges is how to deal with the poor fatigue behaviour of AM material with rough as-built surface.

The aim of this thesis is to increase the knowledge of how AM can be used for high performance industrial parts by investigating the fatigue behaviour of the titanium alloy Ti6Al4V produced with different AM processes. Foremost, the intention is to improve the understanding of how rough as-built AM surfaces in combination with AM built geometrical notches affects the fatigue properties.This was done by performing constant amplitude fatigue testing to compare different combinations of AM material produced by Electron Beam Melting(EBM) and Laser Sintering (LS) with machined or rough as-built surfaces with or without geometrical notches and Hot Isostatic Pressing (HIP) treatment. Furthermore, the material response can be different between constant amplitude and variable amplitude fatigue loading due to effects of overloads and local plastic deformations. The results from constant amplitude testing were used to predict the fatigue life for variable amplitude loading by cumulative damage approach and these predictions were then verified by experimental variable amplitude testing.

The constant amplitude fatigue strength of material with rough as-built surfaces was found to be 65-75 % lower, compared to conventional wrought bar, in which HIP treatments had neglectable influence on the fatigue strength. Furthermore, the fatigue life predictions with cumulative damage calculations showed good agreement with the experimental results which indicates that a cumulative damage approach can be used, at least for a tensile dominated load sequences, to predict the fatigue behaviour of additive manufactured Ti6Al4V.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. p. 50
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1775
National Category
Other Materials Engineering Manufacturing, Surface and Joining Technology Applied Mechanics Composite Science and Engineering Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:liu:diva-137233 (URN)10.3384/lic.diva-137233 (DOI)9789176855386 (ISBN)
Presentation
2017-06-02, ACAS, A-huset, Campus Valla, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2018-01-13Bibliographically approved

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The full text will be freely available from 2019-06-19 15:02
Available from 2019-06-19 15:02

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