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On Residual Stresses in Resistance Spot-Welded Aluminum Alloy 6061-T6: Experimental and Numerical Analysis
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
Iran Univ Sci & Technol, Tehran, Iran.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0003-4180-4710
2013 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 22, no 12, 3612-3619 p.Article in journal (Refereed) Published
Abstract [en]

In this study, an electro-thermal-structural-coupled finite element (FE) model and x-ray diffraction residual stress measurements have been utilized to analyze distribution of residual stresses in an aluminum alloy 6061-T6 resistance spot-welded joint with 2-mm-thickness sheet. Increasing the aluminum sheet thickness to more than 1 mm leads to creating difficulty in spot-welding process and increases the complexity of the FE model. The electrical and thermal contact conductances, as mandatory factors are applied in contact areas of electrode-workpiece and workpiece-workpiece to resolve the complexity of the FE model. The physical and mechanical properties of the material are defined as thermal dependent to improve the accuracy of the model. Furthermore, the electrodes are removed after the holding cycle using the birth-and-death elements method. The results have a good agreement with experimental data obtained from x-ray diffraction residual stress measurements. However, the highest internal tensile residual stress occurs in the center of the nugget zone and decreases toward nugget edge; surface residual stress increases toward the edge of the welding zone and afterward, the area decreases slightly.

Place, publisher, year, edition, pages
2013. Vol. 22, no 12, 3612-3619 p.
Keyword [en]
Al-alloy, finite element analysis, residual stresses, resistance spot welding, x-ray diffraction
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-131316DOI: 10.1007/s11665-013-0657-1ISI: 000328207300002Scopus ID: 2-s2.0-84890988634OAI: oai:DiVA.org:kth-131316DiVA: diva2:655784
Note

QC 20140108

Available from: 2013-10-14 Created: 2013-10-14 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Mechanical Properties of Resistance Spot Welds in Lightweight Applications
Open this publication in new window or tab >>Mechanical Properties of Resistance Spot Welds in Lightweight Applications
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This licentiate thesis is concerned with residual stresses in aluminum alloy 6061-T6 resistance spot welded joint. Several topics related to mechanical strength of welded structures are treated such as; nugget size and microhardness and microstructures of weld zone and their influence on mechanical strength of welded structure, failure load measurement using tensile-shear test, resistance spot welding simulation, residual stress measurement by X-ray diffraction method and analysis effect of welding parameters on the mechanical strength and the residual stresses.

To investigate the effect of resistance spot weld parameters on mechanical strength of welded structures, various welding parameters e.g. welding current, welding time and electrode force are selected to produce welded joints with different quality. According to the failure mode, the empirical equation was used to prediction of failure load base on nugget size and hardness of failure line. Microstructure study has been carried out to investigate microstructural changes in the welded joints. Microhardness tests are done to find hardness profiles due to microstructural changes and determine the minimum hardness.

In addition, an electro-thermal-structural coupled finite element model and X-ray diffraction residual stress measurement have been utilized to analyze residual stresses distribution in weld zone. The electrical and thermal contact conductance, as mandatory factors are applied in contact area between electrode-workpiece and workpiece-workpiece to resolve the complexity of the finite element model. The physical and mechanical properties of the material are defined as thermal-dependent in order to improve the accuracy of the model. Furthermore, the electrodes are removed after holding cycle using the birth and death elements method. Moreover, the effect of welding parameters on maximum residual stress is investigated and a regression model is proposed to predict maximum tensile residual stresses in terms of welding parameters.

The results obtained from the finite element analysis have been used to build up two back-propagation artificial neural network models for the residual stresses and the nugget size prediction. The results revealed that the neural network models created in this study can accurately predict the nugget size and the residual stresses produced in resistance spot weld. Using a combination of these two developed models, the nugget size and the residual stresses can be predicted in terms of spot weld parameters with high speed and accuracy.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. v, 19 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2013:45
Keyword
Spot Weld, Aluminum alloy, Mechanical Properties, Finite Element
National Category
Vehicle Engineering
Research subject
SRA - Production
Identifiers
urn:nbn:se:kth:diva-131306 (URN)978-91-7501-838-6 (ISBN)
Presentation
2013-09-30, M37, Brinellvagen 64, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
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No
Note

QC 20131014

Available from: 2013-10-14 Created: 2013-10-12 Last updated: 2013-10-14Bibliographically approved

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Barsoum, Zuhier

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