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Mi, Y., Guglielmi, P., Nilsen, M., Sikström, F., Palumbo, G. & Ancona, A. (2023). Beam shaping with a deformable mirror for gap bridging in autogenous laser butt welding. Optics and Lasers in Engineering, 169, Article ID 107724.
Open this publication in new window or tab >>Beam shaping with a deformable mirror for gap bridging in autogenous laser butt welding
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2023 (English)In: Optics and Lasers in Engineering, ISSN 0143-8166, Vol. 169, article id 107724Article in journal (Refereed) Published
Abstract [en]

In autogenous laser butt welding the variability of the joint gap can cause problems in terms of weld seam quality. A suitable strategy to alleviate this is to dynamically shape the laser beam instead of a circular-shaped beam with typical Gaussian or top hat distributions. Currently available systems cannot reach sufficient performance due to both the real time control system for the shape variation and the limited laser power currently manageable. In the present work, the possibility of bridging the joint gap during welding using a deformable mirror to elongate the focused laser beam from circular to transversal elliptical shape was investigated. The effect of the beam shaping on the geometry of the weld pool and of the weld cross sections was analysed, for different values of the gap in comparison with a circular Gaussian beam. It was demonstrated that the adoption of a transversal elliptical laser beam makes the welding process more stable, especially for large gaps (i.e. larger than the circular beam radius). Thanks to the beam shaping, the extension of the fused zone (in terms of the cross section area, height and width) resulted to be less sensitive to the gap's dimension; in addition, the extension of the heat affected zone and the presence of undercuts were evidently reduced.

Keywords
Laser beam welding, Beam shaping, Process monitoring, Microstructure, Steel
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-20684 (URN)10.1016/j.optlaseng.2023.107724 (DOI)001041329900001 ()2-s2.0-85164226707 (Scopus ID)
Funder
Knowledge Foundation, 20170315Knowledge Foundation, 20210094
Available from: 2023-12-29 Created: 2023-12-29 Last updated: 2024-03-15Bibliographically approved
Ancona, A., Sikström, F., Christiansson, A.-K., Nilsen, M., Mi, Y. & Kisielewicz, A. (2023). Monitoring and control of directed energy deposition using a laser beam (1.ed.). In: Pederson, Robert, Andersson, Joel & Joshi, Shrikant V. (Ed.), Additive Manufacturing of High-Performance metallic Materials: (pp. 612-638). Elsevier
Open this publication in new window or tab >>Monitoring and control of directed energy deposition using a laser beam
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2023 (English)In: Additive Manufacturing of High-Performance metallic Materials / [ed] Pederson, Robert, Andersson, Joel & Joshi, Shrikant V., Elsevier, 2023, 1., p. 612-638Chapter in book (Refereed)
Abstract [en]

To be a successful competitor among other technologies, metallic laser-directed energy depositionusing a laser beam would benefit from the support of intelligent automation making the processrobust, repeatable, and cost-efficient. This calls for technology leaps towards robust and accuratedetection and estimation of the conditions during processing and control schemes for robustperformance. This chapter discusses how developments in sensor technology and model-basedsignal processing can contribute to advancements in in-process monitoring of directed energydeposition using a laser beam and how developments in model-based feedforward- and feedbackcontrol can support automation. The focus is on how machine vision, optical emission spectroscopy,thermal sensing, and electrical process signals can support monitoring, control and better processunderstanding. These approaches are industrially relevant and have a high potential to support amore sustainable manufacturing. 

Place, publisher, year, edition, pages
Elsevier, 2023 Edition: 1.
Keywords
Directed energy deposition using a laser beam; Electrical process signals; Feedstock wire and powder; Infrared imaging; Machine vision; Model-based control; Photo detection; Radiation pyrometry; Signal processing; Spectroscopy
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-21079 (URN)9780323918855 (ISBN)9780323913829 (ISBN)
Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2024-01-11Bibliographically approved
Kisielewicz, A., Mi, Y., Sikström, F. & Ancona, A. (2023). Multi sensor monitoring  of the wire-melt pool interaction inhot-wire directed energy deposition using laser beam. In: IOP Conference Series: Materials Science and Engineering. Paper presented at NOLAMP 19th Nordic Laser Material Processing Conference 22-24 August 2023 Turku, Finland (pp. 1-11). IOP Publishing, 1296, Article ID 012011.
Open this publication in new window or tab >>Multi sensor monitoring  of the wire-melt pool interaction inhot-wire directed energy deposition using laser beam
2023 (English)In: IOP Conference Series: Materials Science and Engineering, IOP Publishing , 2023, Vol. 1296, p. 1-11, article id 012011Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

This study investigates the combination of three sensors to improve in-process monitoring of the liquid bridge between the feedstock wire and melt pool in hot-wire Directed Energy Deposition using Laser Beam. The stability of the deposition process relies on the transfer of metal between the molten feedstock wire and melt pool. Therefore, monitoring the condition of the liquid bridge and the interaction between the feedstock wire and melt pool is crucial. By utilizing a laser-optics-integrated visible range optical spectrometer and electrical sensors measuring voltage and current, relevant process changes and indications of instabilities were detected. Combined information from the current sensor and the spectrometer provided a better understanding of the process and helped to identify deviations leading to unstable deposition modes.

Place, publisher, year, edition, pages
IOP Publishing, 2023
Keywords
wire-melt, laser beam, multi sensor monitoring
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-20863 (URN)10.1088/1757-899X/1296/1/012011 (DOI)
Conference
NOLAMP 19th Nordic Laser Material Processing Conference 22-24 August 2023 Turku, Finland
Funder
Swedish Research Council, SAMw [20170060]Vinnova, InAIRwire [2019-02752]
Note

CC BY 3.0

Available from: 2024-02-15 Created: 2024-02-15 Last updated: 2024-02-15
Jadidi, A., Mi, Y., Sikström, F., Nilsen, M. & Ancona, A. (2022). Beam Offset Detection in Laser Stake Welding of Tee Joints Using Machine Learning and Spectrometer Measurements. Sensors, 22(10)
Open this publication in new window or tab >>Beam Offset Detection in Laser Stake Welding of Tee Joints Using Machine Learning and Spectrometer Measurements
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2022 (English)In: Sensors, E-ISSN 1424-8220, Vol. 22, no 10Article in journal (Refereed) Published
Abstract [en]

Laser beam welding offers high productivity and relatively low heat input and is one key enabler for efficient manufacturing of sandwich constructions. However, the process is sensitive to how the laser beam is positioned with regards to the joint, and even a small deviation of the laser beam from the correct joint position (beam offset) can cause severe defects in the produced part. With tee joints, the joint is not visible from top side, therefore traditional seam tracking methods are not applicable since they rely on visual information of the joint. Hence, there is a need for a monitoring system that can give early detection of beam offsets and stop the process to avoid defects and reduce scrap. In this paper, a monitoring system using a spectrometer is suggested and the aim is to find correlations between the spectral emissions from the process and beam offsets. The spectrometer produces high dimensional data and it is not obvious how this is related to the beam offsets. A machine learning approach is therefore suggested to find these correlations. A multi-layer perceptron neural network (MLPNN), support vector machine (SVM), learning vector quantization (LVQ), logistic regression (LR), decision tree (DT) and random forest (RF) were evaluated as classifiers. Feature selection by using random forest and non-dominated sorting genetic algorithm II (NSGAII) was applied before feeding the data to the classifiers and the obtained results of the classifiers are compared subsequently. After testing different offsets, an accuracy of 94% was achieved for real-time detection of the laser beam deviations greater than 0.9 mm from the joint center-line.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
laser beam offset; feature selection; laser beam welding; machine learning; spectrometer; tee joint
National Category
Bioinformatics and Systems Biology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-18671 (URN)10.3390/s22103881 (DOI)000803647200001 ()35632290 (PubMedID)2-s2.0-85130378549 (Scopus ID)
Funder
Knowledge Foundation, 20170315
Available from: 2022-06-28 Created: 2022-06-28 Last updated: 2024-04-12
Mi, Y., Mahade, S., Sikström, F., Choquet, I., Joshi, S. V. & Ancona, A. (2022). Conduction mode laser welding with beam shaping using a deformable mirror. Optics and Laser Technology, 148
Open this publication in new window or tab >>Conduction mode laser welding with beam shaping using a deformable mirror
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2022 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 148Article in journal (Refereed) Published
Abstract [en]

This study explores the possibility of tailoring the fusion zone in conduction mode laser welding using a deformable mirror for beam shaping of multi-kilowatt continuous wave laser sources. Three power density distributions were shaped and used in bead on plate welding of Ti64 plates in conduction mode at three travel speeds. The effect on melt pool free surface geometry, cross section, microstructure and hardness profiles was measured and studied. It is shown that the geometry of the melt pool can be modified using a deformable mirror. A narrower and longer melt pool or a wider, shorter and shallower one were indeed obtained forming Gaussian-elliptical power density distributions oriented along and transverse to the travel direction, respectively. The latter distribution could be a favourable option for laser beam additive manufacturing as it could improve process efficiency while reducing remelting of the previous layer. This system has also a promising potential for adaptive process control since it could change fundamentally the beam shape at a rate faster than 10 ms. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2022
Keywords
Adaptive control systems; Continuous wave lasers; Deformation; Gaussian beams; Lakes; Laser beam welding; Laser beams; Laser mirrors; Microstructure, Beam-shaping; Conduction mode; Conduction mode laser welding; Conduction mode welding; Deformable mirrors; Fusion zone geometry; Fusion zones; Melt pool; Melt pool geometry; Power density distributions, Geometry
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17945 (URN)10.1016/j.optlastec.2021.107718 (DOI)000788245300001 ()2-s2.0-85120819958 (Scopus ID)
Funder
Knowledge Foundation, 20170315
Available from: 2022-03-07 Created: 2022-03-07 Last updated: 2024-04-12
Noori Rahim Abadi, S. M., Mi, Y., Sikström, F., Ancona, A. & Choquet, I. (2021). Effect of shaped laser beam profiles on melt flow dynamics in conduction mode welding. International journal of thermal sciences, 166, 1-15, Article ID 106957.
Open this publication in new window or tab >>Effect of shaped laser beam profiles on melt flow dynamics in conduction mode welding
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2021 (English)In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 166, p. 1-15, article id 106957Article in journal (Refereed) Published
Abstract [en]

A computational fluid dynamics approach is used to analyse the influence of beam shaping in fusion welding on melt thermal flow. Three beam shapes are studied at several welding travel speeds: a reference Gaussian profile and its elliptic elongations along and transverse to the welding travel direction. It is found that these beam shapes change not only the intensity and direction of the melt thermocapillary flow but also the flow pattern. For instance, and contrary to the other profiles, the beam shape elongated along the welding travel direction generates melt front vortices that assist metal pre-heating. It can result in deeper penetration, larger melt volume, and lower amount of thermal energy diffused into the heat affected zone. The simple elongation of a beam profile has thus a non-linear effect on the melt flow and in turn on the seam geometry as well as the temperature gradients in the heat affected zone.

Keywords
Laser beam welding, Beam shaping, Phase change, Melt flow, Free surface deformation
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-17409 (URN)10.1016/j.ijthermalsci.2021.106957 (DOI)000645187000002 ()2-s2.0-85103695215 (Scopus ID)
Available from: 2021-09-01 Created: 2021-09-01 Last updated: 2023-01-05Bibliographically approved
Kisielewicz, A., Thalavai Pandian, K., Sthen, D., Hagqvist, P., Valiente Bermejo, M. A., Sikström, F. & Ancona, A. (2021). Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire. Metals, 11(4), 1-25
Open this publication in new window or tab >>Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire
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2021 (English)In: Metals, ISSN 2075-4701, Vol. 11, no 4, p. 1-25Article in journal (Refereed) Published
Abstract [en]

This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
laser-directed energy deposition with wire, laser–metal deposition with wire, hot-wire, resistive pre-heating, in-process monitoring
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-16428 (URN)10.3390/met11040634 (DOI)000643283500001 ()2-s2.0-85104042477 (Scopus ID)
Funder
Vinnova, 2019-02752
Note

Finansiärer:Stiftelsen för Kunskaps- och KompetensutvecklingProjektnummer: 20160281, 20170060

Available from: 2021-04-14 Created: 2021-04-14 Last updated: 2023-10-26
Kisielewicz, A., Sadeghi, E., Sikström, F., Christiansson, A.-K., Palumbo, G. & Ancona, A. (2020). In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718. Materials & design, 186, Article ID 108317.
Open this publication in new window or tab >>In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718
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2020 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, article id 108317Article in journal (Refereed) Published
Abstract [en]

In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

Keywords
Spectroscopic system, Additive manufacturing, Directed energy deposition, Cr depletion, High-temperature corrosion
National Category
Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14733 (URN)10.1016/j.matdes.2019.108317 (DOI)000505221700047 ()2-s2.0-85075265930 (Scopus ID)
Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2023-10-26Bibliographically approved
Elefante, A., Nilsen, M., Sikström, F., Christiansson, A.-K., Maggipinto, T. & Ancona, A. (2019). Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal. Optics and Laser Technology, 109, 178-185
Open this publication in new window or tab >>Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal
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2019 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, p. 178-185Article in journal (Refereed) Published
Abstract [en]

Robotized laser beam welding of closed-square-butt joints is sensitive to the positioning of the laser beam with respect to the joint since even a small offset may result in a detrimental lack of sidewall fusion. An evaluation of a system using a photodiode aligned coaxial to the processing laser beam confirms the ability to detect variations of the process conditions, such as when there is an evolution of an offset between the laser beam and the joint. Welding with different robot trajectories and with the processing laser operating in both continuous and pulsed mode provided data for this evaluation. The detection method uses wavelet analysis of the photodetector signal that carries information of the process condition revealed by the plasma plume optical emissions during welding. This experimental data have been evaluated offline. The results show the potential of this detection method that is clearly beneficial for the development of a system for welding joint tracking.

Keywords
Laser beam welding, Joint tracking, Butt joints, Photodiode, Wavelet analysis
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12832 (URN)10.1016/j.optlastec.2018.08.006 (DOI)000446949600023 ()2-s2.0-85051138319 (Scopus ID)
Funder
Vinnova, 2016-03291
Note

Funding: People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no 608473 (MoRE program project "Hy-Las"

Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2021-02-03Bibliographically approved
Tricarico, L., Ancona, A., Palumbo, G., Sorgente, D., Corizzo, O., Spina, R. & Lugara, P. M. (2019). Numerical and experimental investigation of the discrete spot laser hardening of a graphite-coated hypereutectoid steel using a fibre laser. The International Journal of Advanced Manufacturing Technology, 104(1-4), 1393-1402
Open this publication in new window or tab >>Numerical and experimental investigation of the discrete spot laser hardening of a graphite-coated hypereutectoid steel using a fibre laser
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2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 104, no 1-4, p. 1393-1402Article in journal (Refereed) Published
Abstract [en]

The single-pulse laser hardening of a hypereutectoid steel coated by a graphite layer was investigated using a numerical/experimental approach. Experimental tests were conducted on coated samples using a fibre laser source and without any gas shielding aiming to explore the effect of laser power, pulse energy and defocusing distance on the dimensions of the hardened region. The process operating window of the discrete spot laser hardening using the graphite layer was determined through a finite element model and compared with previous results obtained on uncoated samples. For the same laser power and interaction times, an enlargement of the hardened region was found when using the graphite coating, especially when operating at the lowest laser energy level. The process operating window remains similar in shape to the one of the uncoated steel but moves towards larger hardened diameters and much larger defocusing distances. Once the maximum temperature has been fixed, a linear relationship between the hardened diameter and the defocusing distance exists. No obvious surface oxidation occurs since the graphite coating acts as a protective layer. © 2019, Springer-Verlag London Ltd., part of Springer Nature.

Keywords
Coatings; Fiber lasers; Finite element method; Graphite; Steel fibers, Experimental investigations; Hypereutectoid steel; Laser energy levels; Laser hardening; Linear relationships; Maximum temperature; Surface oxidations; Surface structuring, Hardening
National Category
Manufacturing, Surface and Joining Technology Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-14480 (URN)10.1007/s00170-019-04014-4 (DOI)000483808200100 ()2-s2.0-85068736856 (Scopus ID)
Note

Funders: Italian Ministry of Education, Universities and Research Government  (grants PON01_02584, project acronym: SMATI; PON01_02238, project acronym: EURO6; and PON02_00576_3333604, project acronym: INNOVHEAD)

Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2020-01-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6247-5429

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