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Westerberg, Lars-GöranORCID iD iconorcid.org/0000-0001-5294-1855
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Publications (10 of 98) Show all publications
Westin, E. M. & Westerberg, L.-G. (2024). Evaluation of methods used for simulation of heat-affected zones in duplex stainless steels. Welding in the World
Open this publication in new window or tab >>Evaluation of methods used for simulation of heat-affected zones in duplex stainless steels
2024 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Article in journal (Refereed) Epub ahead of print
Abstract [en]

The weldability of duplex stainless steels partly depends on the ferritization of the high-temperature heat-affected zone (HT-HAZ). This area is rather narrow, and it can be challenging to visualize and determine its actual impact on the properties. To address this, various methods were applied to study the grain growth and austenite reformation in the HT-HAZ of the lean duplex grade UNS S32101. Thermo-mechanical Gleeble® simulations were conducted at 1360 °C with different holding times and cooling rates. Subsequently, the grain size and ferrite content were measured on polished and etched cross-sections. Bead-on-plate welds were performed on the same heat of 6-mm plate thickness using the gas tungsten arc welding (GTAW) process. The shielding gas was Ar + 0–8% N2 to illustrate the effect of nitrogen additions on the HT-HAZ morphology. The arc was either stationary, welding at one spot for 0.5–120 s, or travelling at different speeds to generate varying heat inputs and temperature gradients. The thermo-mechanical simulations approximated the results obtained by travelling arc welding and allowed for a more comprehensive investigation. Stationary arc welding was not suitable for HT-HAZ studies as it quickly caused nitrogen depletion and resulted in significantly higher ferrite contents compared to the travelling arc welds.

Keywords
Duplex stainless steel, Welding, GTAW, HAZ, Nitrogen, Phase balance, Physical simulation
National Category
Manufacturing, Surface and Joining Technology
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-104377 (URN)10.1007/s40194-024-01698-5 (DOI)
Note

Full text license: CC BY

Available from: 2024-02-23 Created: 2024-02-23 Last updated: 2024-02-23
Siddanathi, L. S., Westerberg, L.-G., Åkerstedt, H., Wiinikka, H. & Sepman, A. (2023). Computational Analysis Of Different Non-Transferred Plasma Torch Geometries. In: 2023 IEEE International Conference on Plasma Science (ICOPS): . Paper presented at 50th IEEE International Conference on Plasma Science (ICOPS 50), May 21-25 2023, Santa Fe, New Mexico, USA. IEEE, Article ID P-1.27.
Open this publication in new window or tab >>Computational Analysis Of Different Non-Transferred Plasma Torch Geometries
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2023 (English)In: 2023 IEEE International Conference on Plasma Science (ICOPS), IEEE, 2023, article id P-1.27Conference paper, Poster (with or without abstract) (Other academic)
Place, publisher, year, edition, pages
IEEE, 2023
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-98571 (URN)10.1109/ICOPS45740.2023.10481371 (DOI)2-s2.0-85190617555 (Scopus ID)
Conference
50th IEEE International Conference on Plasma Science (ICOPS 50), May 21-25 2023, Santa Fe, New Mexico, USA
Funder
Swedish Energy Agency, 49609-1
Note

ISBN for host publication: 979-8-3503-0266-0; 

Available from: 2023-06-19 Created: 2023-06-19 Last updated: 2024-05-08Bibliographically approved
Siddanathi, L. S., Westerberg, L.-G., Åkerstedt, H. O., Wiinikka, H. & Sepman, A. (2023). Computational modeling and temperature measurements using emission spectroscopy on a non-transferred plasma torch. AIP Advances, 13(2), Article ID 025019.
Open this publication in new window or tab >>Computational modeling and temperature measurements using emission spectroscopy on a non-transferred plasma torch
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2023 (English)In: AIP Advances, E-ISSN 2158-3226, Vol. 13, no 2, article id 025019Article in journal (Refereed) Published
Abstract [en]

A non-transferred plasma torch is a device used to generate a steady thermal plasma jet. Plasma torches have the potential to replace fossil fuel burners used as heat sources in the process industry. Today, however, the available plasma torches are of small scale compared to the power used in the burners in the process industry. In order to understand the effects of large scales on the plasma flow dynamics, it is essential to understand the operation of the plasma torch under different operating conditions and for different geometries. In this study, the analysis of a non-transferred plasma torch has been carried out using both computational and experimental methods. Computationally, the magnetohydrodynamic (MHD) equations are solved using a single-fluid model on a 2D axisymmetric torch geometry. The experiments are performed using emission spectroscopy to measure the plasma jet temperature at the outlet. This paper explains the changes in the arc formation, temperature, and velocity for different working gases and power inputs. Furthermore, the possibilities and disadvantages of the MHD approach, considering a local thermal equilibrium, are discussed. It was found that in general, the computational temperature obtained is supported by the experimental and equilibrium data. The computational temperatures agree by within 10% with the experimental ones at the center of the plasma torch. The paper concludes by explaining the significant impact of input properties like working gas and power input on the output properties like velocity and temperature of plasma jet. 

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2023
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-95556 (URN)10.1063/5.0129653 (DOI)000926849300042 ()2-s2.0-85147798595 (Scopus ID)
Funder
Swedish Energy Agency, 49609-1
Note

Validerad;2023;Nivå 2;2023-02-08 (johcin)

Available from: 2023-02-08 Created: 2023-02-08 Last updated: 2024-03-07Bibliographically approved
Siddanathi, L. S., Westerberg, L.-G., Åkerstedt, H. O., Wiinikka, H. & Sepman, A. (2023). Computational Modeling of a Plasma Torch Using Single-Fluid and Two-Fluid Modeling Approaches. In: COMSOL Conference 2023: . Paper presented at COMSOL Conference 2023, Munich, Germany, October 25–27, 2023. COMSOL
Open this publication in new window or tab >>Computational Modeling of a Plasma Torch Using Single-Fluid and Two-Fluid Modeling Approaches
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2023 (English)In: COMSOL Conference 2023, COMSOL , 2023Conference paper, Published paper (Refereed)
Abstract [en]

Plasma, a complex fluid consisting of electrons, ions, neutrals, and excited species, exhibits both fluid-like behavior and electrical conductivity due to the presence of charge carriers. Consequently, computational modeling of plasma requires the integration of fluid and electrical models. This research paper presents a study on the steady-state computational modeling of a plasma torch with a 2D axisymmetric geometry using single-fluid and two-fluid modeling approaches in the COMSOL Multiphysics® software. The single-fluid modeling (SFM) approach combines the individual equations governing the behavior of different particles into a unified equation. Specifically, the SFM approach utilized in this study focuses on a fully ionized plasma and employs the Magnetohydrodynamic equations whose adaptation is equilibrium discharge interface (EDI) model available in COMSOL Multiphysics®. The EDI model solves the magnetohydrodynamic (MHD) equations, encompassing electric and magnetic fields, heat transfer in solids and fluids, and laminar models. By employing this approach, the researchers simulated and analyzed the behavior of the plasma torch. In contrast, the two-fluid modeling (TFM) approach separates the fluid equations for electrons and ions, considering a weakly ionized plasma. The TFM model is developed by deriving fluid equations based on kinetic theory for neutrals, ions, and electrons. These equations are then implemented in COMSOL Multiphysics®, utilizing models for the transport of diluted species, laminar flow, heat transfer in solids and fluids, and electric and magnetic fields. By adopting the TFM approach, the researchers aimed to gain insights into the behavior of the plasma torch. Throughout the study, various properties such as temperature, velocity, current density, and particle concentrations are analyzed within the plasma torch. Results obtained from both the single-fluid and two-fluid modeling approaches are compared and evaluated. This comparative analysis allows the researchers to highlight the advantages and challenges associated with each modeling approach. In conclusion, this study contributes to understanding plasma behavior by employing computational modeling techniques. The research presents and compares the outcomes of single-fluid and two-fluid modeling approaches applied to a plasma torch. By examining the advantages and challenges of each approach, the study offers valuable insights for future plasma modeling endeavors.

Place, publisher, year, edition, pages
COMSOL, 2023
Keywords
non-transferred plasma torch, Magnetohydrodynamics, weak ionization
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-102509 (URN)
Conference
COMSOL Conference 2023, Munich, Germany, October 25–27, 2023
Funder
Swedish Energy Agency, 49609-1
Available from: 2023-11-20 Created: 2023-11-20 Last updated: 2024-02-09Bibliographically approved
Giacomini, E., Westerberg, L.-G. & Nikolakopoulos, G. (2022). A Survey on Drones for Planetary Exploration: Evolution and Challenges. In: 2022 30th Mediterranean Conference on Control and Automation (MED): . Paper presented at 30th Mediterranean Conference on Control and Automation (MED), Vouliagmeni, Greece, June 28 - July 1, 2022 (pp. 583-590). IEEE
Open this publication in new window or tab >>A Survey on Drones for Planetary Exploration: Evolution and Challenges
2022 (English)In: 2022 30th Mediterranean Conference on Control and Automation (MED), IEEE, 2022, p. 583-590Conference paper, Published paper (Refereed)
Abstract [en]

During the last decade, the efforts in space exploration have increased massively and led to a need for new ways to examine planets and other celestial bodies. The modern tendency is to create spacecraft able to scout the surface from a higher point of view, where drones have shown to be most helpful. Even if the benefits brought by this type of technology are considerable, the challenges are still difficult to overcome. This article presents a comprehensive literature review on drone technologies for planetary exploration, focusing mainly on the difficulties encountered. Considerable complications derive from the unknown environment, affecting most of the design, the mathematical model of the body, its controllability, and overall levels of autonomy. Various solutions to these challenges are proposed based on past and future missions. Furthermore, a look into the future gives an idea of possible technological developments and ways to provide the most efficient aerial exploration of other planets.

Place, publisher, year, edition, pages
IEEE, 2022
Series
Mediterranean Conference on Control and Automation (MED), ISSN 2325-369X, E-ISSN 2473-3504
National Category
Robotics Aerospace Engineering
Research subject
Robotics and Artificial Intelligence; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-92638 (URN)10.1109/MED54222.2022.9837214 (DOI)000854013700096 ()2-s2.0-85136272433 (Scopus ID)
Conference
30th Mediterranean Conference on Control and Automation (MED), Vouliagmeni, Greece, June 28 - July 1, 2022
Note

ISBN för värdpublikation: 978-1-6654-0673-4 (electronic), 978-1-6654-0674-1 (print)

Available from: 2022-08-23 Created: 2022-08-23 Last updated: 2023-09-05Bibliographically approved
Likitha, S. S., Westerberg, L.-G., Akerstedt, H. O., Wiinikka, H. & Sepman, A. (2022). Computational and Experimental Study of Flow Properties in a Plasma Torch. In: Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson (Ed.), Svenska Mekanikdagar 2022: . Paper presented at Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022. Luleå tekniska universitet
Open this publication in new window or tab >>Computational and Experimental Study of Flow Properties in a Plasma Torch
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2022 (English)In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2022
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-95144 (URN)
Conference
Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022
Available from: 2023-01-03 Created: 2023-01-03 Last updated: 2023-10-31Bibliographically approved
Siddanathi, L. S., Westerberg, L.-G., Åkerstedt, H., Wiinikka, H. & Sepman, A. (2022). Computational modeling of a plasma torch using a two-fluid modeling approach. In: 2022 IEEE International Conference on Plasma Science (ICOPS): . Paper presented at 49th International Conference on Plasma Science (ICOPS-2022), Seattle, USA, May 22-26, 2022. IEEE
Open this publication in new window or tab >>Computational modeling of a plasma torch using a two-fluid modeling approach
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2022 (English)In: 2022 IEEE International Conference on Plasma Science (ICOPS), IEEE, 2022Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
IEEE, 2022
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-89927 (URN)10.1109/ICOPS45751.2022.9813023 (DOI)978-1-6654-7925-7 (ISBN)
Conference
49th International Conference on Plasma Science (ICOPS-2022), Seattle, USA, May 22-26, 2022
Funder
Swedish Energy Agency, 49609-1
Available from: 2022-03-28 Created: 2022-03-28 Last updated: 2023-10-31Bibliographically approved
Giacomini, E., Westerberg, L.-G. & Nikolakopoulos, G. (2022). Drones for Planetary Exploration: Modeling Challenges. In: Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson (Ed.), Svenska Mekanikdagar 2022: . Paper presented at Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Drones for Planetary Exploration: Modeling Challenges
2022 (English)In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå: Luleå tekniska universitet, 2022Conference paper, Oral presentation with published abstract (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2022
National Category
Computer Vision and Robotics (Autonomous Systems) Vehicle Engineering
Research subject
Fluid Mechanics; Robotics and Artificial Intelligence
Identifiers
urn:nbn:se:ltu:diva-91536 (URN)
Conference
Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022
Available from: 2022-06-17 Created: 2022-06-17 Last updated: 2023-09-05Bibliographically approved
Farré-Lladós, J., Westerberg, L.-G., Casals-Terré, J., Leckner, J. & Westbroek, R. (2022). On the Flow Dynamics of Polymer Greases. Lubricants, 10(4), Article ID 66.
Open this publication in new window or tab >>On the Flow Dynamics of Polymer Greases
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2022 (English)In: Lubricants, ISSN 2075-4442, Vol. 10, no 4, article id 66Article in journal (Refereed) Published
Abstract [en]

In this paper, the flow dynamics of polymer greases was investigated using micro-particle image velocimetry. Polymer greases have a different thickener structure, compared to widely used lithium-based greases, and they have the well-known ability to release oil. How these properties affect grease deformation and its ability to flow is investigated and compared to the corresponding behavior of a lithium complex grease with the same consistency. Two main tests were carried out, where velocity profiles in a straight channel were measured and analyzed, and velocity evolution during the transition period from a no-flow to a fully-established flow was measured, respectively. It was found that the polymer grease flow dynamics is different from that of the lithium grease. This indicates that the internal structure of the grease and the grease ability to bleed oil have a strong influence on the deformation on a global scale, which in turn entails other lubricating abilities for the two grease types.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
lubricating grease, polymer thickener, lithium grease, flow dynamics, rheology, micro-particle image velocimetry, oil bleeding, transitional flow
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-90217 (URN)10.3390/lubricants10040066 (DOI)000785092900001 ()2-s2.0-85129168769 (Scopus ID)
Note

Validerad;2022;Nivå 2;2022-04-19 (sofila)

Available from: 2022-04-19 Created: 2022-04-19 Last updated: 2023-09-05Bibliographically approved
Jonsén, P., Westerberg, L.-G., Larsson, S. & Olsson, E. (Eds.). (2022). Svenska Mekanikdagar 2022. Paper presented at Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022. Luleå tekniska universitet
Open this publication in new window or tab >>Svenska Mekanikdagar 2022
2022 (English)Conference proceedings (editor) (Refereed)
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2022. p. 104
National Category
Applied Mechanics Fluid Mechanics and Acoustics
Research subject
Solid Mechanics; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-95050 (URN)
Conference
Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022
Available from: 2022-12-29 Created: 2022-12-29 Last updated: 2023-09-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5294-1855

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