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  • 1.
    Ancona, Antonio
    et al.
    University West, Department of Engineering Science, Division of Production Systems. Physics Department, University of Bari ALDO MORO, Bari (ITA).
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Nilsen, Morgan
    University West, Department of Engineering Science, Division of Production Systems.
    Mi, Yongcui
    University West, Department of Engineering Science, Division of Production Systems.
    Kisielewicz, Agnieszka
    University West, Department of Engineering Science, Division of Production Systems.
    Monitoring and control of directed energy deposition using a laser beam2023In: 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. 

  • 2.
    Kisielewicz, Agnieszka
    University West, Department of Engineering Science, Division of Production Systems.
    Towards multi-sensor monitoringand control of Directed Energy Deposition using a Laser Beam2023Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In recent years, an extensive effort has been made to leap European aviation towards more sustainable transportation. Conventional manufacturing methods used in aerospace industry require significant amounts of raw materials, whose extraction, processing, and utilization have adverse environmental impacts. Thus, there is a strong motivation to develop novel, more material efficient fabrication methods. Additive Manufacturing (AM), also known as 3D-printing, offers the advantage of manufacturing near-net-shape structures by adding material only where it is needed, minimizing waste, and improving material efficiency. However, introducing AM fabricated structures as components in safety-critical aerospace systems poses a significant challenge due to the inherent complexity of AM processes. This complexity can result in variations that may lead to defects or inconsistencies in the fabricated structures. Thus, increasing automation by developing in-process monitoring, and control solutions is the vital step to reach the necessary reliability and repeatability.

    This thesis presents development towards multi-sensor monitoring and control of Directed Energy Deposition (DED) using a Laser Beam (LB). DED-LB is an advanced technology that allows to manufacture large-scale, near-net-shape metallic parts. In this work, in-process monitoring solutions for DED-LB with feedstock powder and wire were investigated. The set-up of the latter was complemented by resistive pre-heating of the feedstock wire (hot-wire) which provided means of fine-tuning the heat input and improving metal fusion. Formonitoring purposes, three different in-situ techniques were investigated to monitor process stability and variability. Machine vision and electrical sensing were utilized during DED-LB with feedstock wire (DED-LB/w) depositions,while optical emission spectroscopy was used for monitoring processes with feedstock powder (DED-LB/p) as well as wire. A multi-sensorsystem based on the three sensing technologies was tested during DED-LB/w depositions. The vision system gave clear indications of variations from nominal conditions. Voltage and current sensors indications correlated to changes in process parameters and reflected well the metal transfer (liquid bridge) condition.The spectrometer system indicated well changes related to heat input. In addition, analysis of obtained spectra allowed to detect losses of vital alloying element during DED-LB/p. The main conclusion from the results underlines the need for simultaneous multi-sensor monitoring as it allows not only to detect and estimate process changes but also to better interpret their root causes. Such setup will positively enable a future robust, fault tolerant control system.

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  • 3.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Mi, Yongcui
    University West, Department of Engineering Science, Division of Production Systems.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. Physics Department, University of Bari, Bari (ITA).
    Multi sensor monitoring  of the wire-melt pool interaction inhot-wire directed energy deposition using laser beam2023In: IOP Conference Series: Materials Science and Engineering, IOP Publishing , 2023, Vol. 1296, p. 1-11, article id 012011Conference paper (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.

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  • 4.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Palumbo, Gianfranco
    CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy (ITA).
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy (ITA).
    In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 7182020In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, article id 108317Article in journal (Refereed)
    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.

  • 5.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems.
    Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 7182018In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 418-425Article in journal (Refereed)
    Abstract [en]

    Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

  • 6.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Thalavai Pandian, Karthikeyan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sthen, Daniel
    GKN Aerospace Sweden AB,Trollhättan, Sweden.
    Hagqvist, Petter
    University West, Department of Engineering Science, Division of Production Systems. Procada AB, Trollhättan.
    Valiente Bermejo, María Asunción
    University West, Department of Engineering Science, Division of Welding Technology.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. University of Bari, Physics Department, Bari, (ITA).
    Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire2021In: Metals, ISSN 2075-4701, Vol. 11, no 4, p. 1-25Article in journal (Refereed)
    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.

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  • 7.
    Noori Rahim Abadi, Seyyed Mohammad Ali
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Mi, Yongcui
    University West, Department of Engineering Science, Division of Production Systems.
    Kisielewicz, Agnieszka
    University West, Department of Engineering Science, Division of Production Systems.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of laser-wire interaction on heat and metal transfer in directed energy deposition2023In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 205, article id 123894Article in journal (Refereed)
    Abstract [en]

    In this study, laser metal fusion with feedstock wire is addressed. We investigated how various process parameters affect the fraction of beam energy that is absorbed by the wire and the workpiece and the metal transfer from the feedstock wire to the melt pool. To perform this research, a thermo-fluid dynamic model with tracking of free surface deformation was developed to include the feeding of a solid wire and predict its melting. The fraction of beam energy absorbed by the metal was modeled as a function of local surface curvature and temperature, accounting for multiple Fresnel reflections and absorptions. The model was applied to Titanium alloy (Ti-6Al-4V) with a 1.07 μm laser and a process in conduction mode. Experiments at various wire feeding rates were conducted to evaluate the model’s ability to predict the process and a good agreement was obtained. The different parameters studied were the beam angular position, the wire angular position, the wire feed rate, and the beam-wire offset. The analysis of the simulation results gave a detailed physical understanding of the laser energy use. It highlighted that thermocapillary and Rayleigh-Plateau instabilities can contribute to the transition from continuous to drop metal transfer mode. Damping these instabilities might thus allow using a wider process window.

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  • 8.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Thalavai Pandian, Karthikeyan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Axelsson, Björn
    Alfa Laval Tumba AB, Tumba .
    Harati, Ebrahim
    University West, Department of Engineering Science, Division of Welding Technology. ITW Welding AB, Partille .
    Kisielewicz, Agnieszka
    University West, Department of Engineering Science, Division of Production Systems.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Microstructure of laser metal deposited duplex stainless steel: Influence of shielding gas and heat treatment2021In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 65, p. 525-541Article in journal (Refereed)
    Abstract [en]

    This research work is the first step in evaluating the feasibility of producing industrial components by using Laser Metal Deposition with duplex stainless steel Wire (LMDw). The influence of Ar and N2 shielding gases was investigated in terms of nitrogen loss and in the microstructure and austenite content of different deposited geometries. The evolution of the microstructure in the build-up direction of the Ar and N2-shielded blocks was compared in the heat-treated and as-deposited conditions. The susceptibility for oxygen pick-up in the LMDw deposits was also analyzed, and oxygen was found to be in the range of conventional gas-shielded weldments. Nitrogen loss occurred when Ar-shielding was used; however, the use of N2-shielding prevented nitrogen loss. Austenite content was nearly doubled by using N2-shielding instead of Ar-shielding. The heat treatment resulted in an increase of the austenite content and of the homogeneity in the microstructure regardless of the shielding gas used. The similarity in microstructure and the low spread in the phase balance for the as-deposited geometries is a sign of having achieved a stable and consistent LMDw process in order to proceed with the build-up of more complex geometries closer to industrial full-size components.

1 - 8 of 8
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