Change search
Link to record
Permanent link

Direct link
BETA
Publications (3 of 3) Show all publications
Andersson, O., Fahlström, K. & Melander, A. (2018). Experiments and efficient simulations of distortions of laser beam–welded thin-sheet close beam steel structures. Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, 233(3), 787-796
Open this publication in new window or tab >>Experiments and efficient simulations of distortions of laser beam–welded thin-sheet close beam steel structures
2018 (English)In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 233, no 3, p. 787-796Article in journal (Refereed) Published
Abstract [en]

In this article, geometrical distortions of steel structures due to laser beam welding were analyzed. Two 700-mm-long U-beam structures were welded in overlap configurations: a double U-beam structure and a U-beam/flat structure. The structures were in different material combinations from mild steel to ultrahigh-strength steel welded with different process parameters. Different measures of distortions of the U-beam structures were evaluated after cooling. Significant factors of the welding process and the geometry of the structures were identified. Furthermore, welding distortions were modeled using two predictive finite element simulation models. The previously known shrinkage method and a newly developed time-efficient simulation method were evaluated. The new model describes the effects of expansion and shrinkage of the weld zone during welding and material plasticity at elevated temperatures. The new simulation method has reasonable computation times for industrial applications and improved agreement with experiments compared to the often used so-called shrinkage method.

Keywords
distortions, finite element simulations, Laser beam welding, thin-sheet structures, ultrahigh-strength steel, Distortion (waves), High strength steel, Laser beams, Shrinkage, Steel structures, Thermal barrier coatings, Welds, Efficient simulation, Expansion and shrinkage, Finite element simulation model, Geometrical distortion, Material combination, Ultra high strength steel, Finite element method
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-34551 (URN)10.1177/0954405417749625 (DOI)2-s2.0-85045056604 (Scopus ID)
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2019-05-27Bibliographically approved
Fahlström, K., Andersson, O., Melander, A., Karlsson, L. & Svensson, L.-E. -. (2017). Correlation between laser welding sequence and distortions for thin sheet structures. Science and technology of welding and joining, 22(2), 150-156
Open this publication in new window or tab >>Correlation between laser welding sequence and distortions for thin sheet structures
Show others...
2017 (English)In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 22, no 2, p. 150-156Article in journal (Refereed) Published
Abstract [en]

Thin ultra-high strength steel shaped as 700 mm long U-beams have been laser welded in overlap configuration to study the influence of welding sequence on distortions. Three different welding directions, three different energy inputs as well as stitch welding have been evaluated, using resistance spot welding (RSW) as a reference. Transverse widening at the ends and narrowing at the centre of the beam were measured. A clear correlation was found between the weld metal volume and distortion. For continuous welds there was also a nearly linear relationship between the energy input and distortion. However, the amount of distortion was not affected by a change in welding direction. Stitching and RSW reduced distortion significantly compared to continuous laser welding.

Keywords
Automotive, Distortion, High strength steel, Laser welding, Welding sequence, Distortion (waves), Joints (structural components), Laser beam welding, Resistance welding, Spot welding, Welding, Welds, Continuous laser welding, Linear relationships, Resistance spot welding, Thin-sheet structures, Ultra high strength steel, Welding directions, Welding sequences
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-29342 (URN)10.1080/13621718.2016.1207046 (DOI)2-s2.0-84978705979 (Scopus ID)
Available from: 2017-05-08 Created: 2017-05-08 Last updated: 2019-07-02Bibliographically approved
Torkamany, M. J., Kaplan, A. F. H., Ghaini, F. M., Vänskä, M., Salminen, A., Fahlström, K. & Hedegård, J. (2015). Wire deposition by a laser-induced boiling front (ed.). Optics and Laser Technology, 69, 104-112
Open this publication in new window or tab >>Wire deposition by a laser-induced boiling front
Show others...
2015 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 69, p. 104-112Article in journal (Refereed) Published
Abstract [en]

In laser materials processing the addition of material by wire is an option for techniques like laser welding, laser cladding or rapid prototyping. The stability of the wire deposition is strongly dependent on the wire interaction with the laser beam. For leading position wire feeding, high speed imaging was applied to study the melt transfer from the wire tip to the workpiece during keyhole welding. The observations revealed that a very stable concave processing front forms at the wire tip. A boiling front is established as an extension of the keyhole and the melt film at the front is sheared downwards by the ablation pressure of boiling. The deposition of the molten wire into the weld zone is smooth and controllable. Various wire front geometries and melt transitions are compared for different parameters. The option of laterally oscillating the laser beam is investigated and the interaction mechanism involved is discussed. Wire deposition by inducing a boiling front is explained here for the first time, which should promote future applications use of this very promising technique.

Keywords
Laser welding with Filler wire, Laser beam oscillation, High speed imaging
National Category
Materials Engineering
Identifiers
urn:nbn:se:ri:diva-12777 (URN)10.1016/j.optlastec.2014.12.013 (DOI)2-s2.0-84921027104 (Scopus ID)
Available from: 2016-09-22 Created: 2016-09-22 Last updated: 2019-07-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8933-6720

Search in DiVA

Show all publications
v. 2.35.7