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Influence of fabrication stresses on fatigue life of friction stir welded aluminium profiles
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.ORCID iD: 0000-0002-8494-3983
2012 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, Vol. 212, no 7, 1488-1494 p.Article in journal (Refereed) Published
Abstract [en]

Influence of clamping and welding procedure on fatiguelife of a frictionstir (FS) weldedaluminiumprofile has been analysed. Two series of aluminiumprofiles (series A and B) have been fatigue tested. The different clamping conditions in series A and B gave rise to different failure positions that could not be explained neither by the effective notch stress method, nor by the critical distance methods. The clamping in series A introduced plastic deformation at the weld notch that gave rise to tensile residual stresses. The failure position could be explained from the value of the stress intensity factor provided that the residual stresses were considered.

Place, publisher, year, edition, pages
2012. Vol. 212, no 7, 1488-1494 p.
Keyword [en]
Friction stir welding, Clamping loads, Residual stresses, Stress ratio, Fatigue failure
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-92217DOI: 10.1016/j.jmatprotec.2012.02.008ISI: 000304020800005ScopusID: 2-s2.0-84858304916OAI: diva2:512798
QC 20120329Available from: 2012-03-29 Created: 2012-03-29 Last updated: 2012-06-07Bibliographically approved
In thesis
1. Fatigue Assessment of Friction Stir Welded Joints in Aluminium Profiles
Open this publication in new window or tab >>Fatigue Assessment of Friction Stir Welded Joints in Aluminium Profiles
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Friction stir welding (FSW) is a low heat input solid state welding technology. It is often used for fabrication of aluminium alloys in transportation applications including railway, shipbuilding, bridge structures and automotive components. In these applications the material is frequently subject to varying load conditions and fatigue failure is a critical issue. In most cases standard codes and fatigue guidelines for aluminium welded joints address only welded structures with conventional welding methods but not those with FSW procedure. In the scope of this thesis fatigue life assessment of friction stir welded components was performed using theoretical approaches along with finite element method (FEM). The further aim of this study was to generate a basis for standardization of fatigue assessment of friction stir welded joints.

Friction stir welded hollow aluminium panels of alloy 6005A are investigated. The panels are used for train wall sides, train floors, deck and bridges. Each panel is made of several profiles that are joined with the friction stir welding method. Fatigue bending tests were performed for profiles in these panels. Fatigue cracks and failure appeared at notches in the profiles. With FEM simulations critical positions for crack initiation and failure were identified. The method of critical distance was used to analyse and estimate the fatigue life. It was shown that the failure location and fatigue limit could be predicted for both base metal and weld location. Choice of welding procedure (clamping condition) can significantly influence the fatigue life. It was shown that for some panels the critical distance method was not able to explain the failure in the weld. In this case fracture mechanics together with residual stress analysis were used successfully to predict the failure.

Assuming homogeneous material properties throughout the weld and the base material, FEM analysis for T and overlap joints as well can provide a reasonable fatigue prediction. This suggests that the same assumption can be extended to complex components for failure analysis of the friction stir welded joints when using the critical distance method.

Fatigue assessment of friction stir welded joints was also performed using standard codes Eurocode 9 and IIW. Fatigue curves of traditional fusion welded joints were used. The results are in reasonable agreement with experimental data and FEM predictions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. vii, 45 p.
Friction stir welding, Fatigue, Aluminium alloys, Critical distance, Finite element method, Standard codes
National Category
Manufacturing, Surface and Joining Technology
urn:nbn:se:kth:diva-92157 (URN)978-91-7501-291-9 (ISBN)
Public defence
2012-04-26, Sal F3, Lindstedsvägen 26, KTH, Stockholm, 10:00 (English)
QC 20120330Available from: 2012-03-30 Created: 2012-03-27 Last updated: 2012-04-02Bibliographically approved

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Mahdavi Shahri, MeysamSandström, Rolf
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