I projektet har ett flertal publikationer blivit publicerade eller är inlämnade för publicering.
Antalet tidskriftspublikationer är 4st och antalet konferenspublikationer är 1st.
7.1 Publikationslista
Endast titel och en sammanfattning tas upp i detta kapitel. Då publiceringstiden för en tidskriftsartikel är ca 6 månader finns endast konferensartikeln publicerad. Endast utkast till de övriga bifogas.
[1]
Tidskrift: J. Phys. D: Appl. Phys.
Titel: Redistribution of the melt flow by edge tolerances in laser hybrid welding Författare: J Lamas1, J Karlsson2, P Norman2, A F H Kaplan2 and A Yañez3
1Centro Tecnol´oxico do Naval Galego, Ferrol 15590 (A Coruña) Spain E-mail:jlamas@udc.es
2Luleå University of Technology, Dept. TFM, SE-971 87 Luleå, Sweden E-mail:jan.karlsson@ltu.se
3Centro de Investigaci´ons Tecnol´oxicas, Universidade da Coruña, Ferrol 15403 (A Coruña) Spain E-mail: ayanez@udc.es
Abstract:Hybrid laser-arc welding has high potential to tolerate geometrical edge
uncertainties. Of crucial importance is the melt flow that redistributes the joint edges and the wire electrode to the resolidifying weld surface shape. For a butt joint the industrial joint edge variations can be reduced to three local properties, namely the gap width, the vertical surface position and the vertical edge mismatch. The impact of each property on the resulting weld shape was studied systematically. By triangulation the original edges as well as the resulting weld surface shape were scanned in three dimensions, to study trends.
During hybrid welding at the top surface the melt flow and the electric arc were observed by high speed imaging to analyse the complex fluid flow phenomena. For increasing gap width a linear regime lowering the weld top is followed by lack of penetration of two types. Too high and too low surface position causes different humping instabilities. Too large vertical edge mismatch pronounces an undercut.
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Tidskrift: Applied Surface Science
Titel: Two kinds of undercuts distinguished by their oxides in laser hybrid welding Författare: J. Karlsson1, P. Norman1, A.F.H. Kaplan1
1Luleå University of Technology, Luleå, Sweden
Abstract:Two different types of undercuts have been identified in the cases of remaining or removed mill scale (surface oxides from hot rolling), respectively, when laser hybrid arc welding. The two undercut types are examined by macrographs, SEM and EDX. In both cases Fe- and Si-oxides cover the heated and melted surface. For the mill scale case, in addition much MnO is found in the undercut region. Here the fusion zone suffers from lack of fusion to the melted base material due to the oxides. High speed imaging reveals that the melt adheres at the top surface in case of removed mill scale but glides down when the mill scale is present. The latter causes poor weld quality due to sharper undercut geometry and lack of fusion, compared to having the mill scale removed.
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[3]
Tidskrift: Applied Surface Science
Titel: Observation of the mechanisms causing two kinds of undercuts during laser hybrid arc welding
Författare: J. Karlsson1, P. Norman1, A.F.H Kaplan1, P. Rubin2, J. Lamas1,3, A. Yañez4
1Luleå University of Technology, Dept. TVM, SE-971 87 Luleå, Sweden, www.ltu.se/tfm/produktion
2Rubin-Materialteknik. Consultant. Gullhönevägen 13 97596 Luleå, Sweden
3Centro Centro Tecnolóxico do Naval Galego, Ferrol 15590 (A Coruña) Spain
4Centro Centro de Investigacións Tecnolóxicas, Universidade da Coruña, Ferrol 15403 (A Coruña) Spain
Abstract:Two different kinds of undercuts were identified for the cases of remaining or removed mill scale (surface oxides from hot rolling of steel), respectively, when laser hybrid arc welding. Due to the surface oxides the pulsed leading arc is disturbed and confined, causing a more narrow gouge than without surface oxides. As observed by high speed imaging, the increased arc pressure pushes more strongly on the melt, enabling gouge rim oxidation. The incoming drops try to climb up the rear wall of the gouge, where they adhere in the case of removed oxides, forming slightly curved undercuts by an interface layer. In case of an Mn-oxidized rim the melt glides down again, causing a sharper and lower undercut with lack of fusion. Subsequently, for both cases, along the tail the melt pool slows down and grows the central reinforcement. Consequently, removal of the surface oxides leads to less severe weld undercuts.
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[4]
Tidskrift: Science and Technology of Welding and Joining
Titel: Hybrid fibre-laser welding of 10mm, high-strength, cold forming steel, DOMEX 420MC Författare: Peter M. Norman1, Jan Karlsson1, Javier Lamas2, Alexander F.H. Kaplan1, Armando Yañez2, John Powell1
1Luleå University of Technology, Sweden
2Universidade da Coruña, Spain
Abstract:The hybrid welding process is being used more in industry and as it is a complex process where two different processes are to work together the setup is of utmost
importance. Hybrid laser welding is here represented by an electric-arc torch and a 15kW fibre-laser. The main obstacle for this processing method is to find optimum parameters for each setup and therefore it consumes time that could be used for production instead.
The here presented research is a result of 30 welding trials performed to optimise welding of a truck support axle. The results are generalised to facilitate understanding and to enable use of the results in oncoming hybrid laser welding trials. In the data, tacit knowledge is also included. This is a type of knowledge that is difficult to get in writing as it is hidden as thoughts and expertise of the operator. The results emanate in a MatrixFlowChart (MFC), which facilitates understanding of the welding results.
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[5]
Konferens: LANE 2010 Conference, Laser and Net Shape Engineering, Erlangen, Tyskland Titel: Classification and generalization of data from a fibre-laser hybrid welding case Författare: Peter M. Norman, Alexander F.H. Kaplan, Jan Karlsson
Luleå University of Technology, Luleå 97187, Sweden
Abstract:Compared to autonomous laser welding, the amount of parameters is higher for laser hybrid welding. Consequently, empirical optimisation of these parameters is a challenge. Handling and evaluation at a higher systematic level is desired in order to enhance the ability to build research on previous knowledge. Such new approach is studied on a case with 10 mm high strength steel sheets, fibre-laser hybrid welded. Aim of the paper is to provide a method of documenting and handling data, transferable to other disciplines, to continuously build knowledge, to simplify repetition of experiments and to facilitate the start-up phase of new trials. Starting from 30 experimental results depending on 23 parameters, by the Matrix Flow Chart a guideline has been developed that filters the information through combination, priorities and quality categorization. A chart resulted where five categories of poor quality are graphically related to a high quality category which can be achieved when following the guidelines for eight main arc- or laser-parameters. The chart is a guideline suitable for extension and for exploring the limits of its validity.
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