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Svahn, F., Mishra, P., Edin, E., Åkerfeldt, P. & Antti, M.-L. (2024). Microstructure and mechanical properties of a modified 316 austenitic stainless steel alloy manufactured by laser powder bed fusion. Journal of Materials Research and Technology, 28, 1452-1462
Open this publication in new window or tab >>Microstructure and mechanical properties of a modified 316 austenitic stainless steel alloy manufactured by laser powder bed fusion
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2024 (English)In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 28, p. 1452-1462Article in journal (Refereed) Published
Abstract [en]

A 316 austenitic stainless-steel alloy, with modified alloy composition, manufactured by laser powder bed fusion (L-PBF) has been investigated. The modification of the alloy composition included addition of niobium (Nb), tungsten (W) and copper (Cu), together with a reduction in the amount of molybdenum (Mo) and an increased amount of carbon (C). To find suitable process parameters, a parameter study by varying laser power, hatch distance and scan speed was performed, centered on typical parameters used for normal 316 L. As-built material from a selected parameter configuration was then subjected to different stress relief annealing heat treatments and ageing heat treatments. The effectiveness of the stress annealing was ranked using a deformation-based method. Microstructural characterization, hardness and room temperature tensile testing were done to evaluate the effect of stress relief and aging heat treatments.

It was found that a higher volumetric energy was needed to build dense material, about ∼50 % higher compared to the volumetric energy input for normal 316 L. A subsequent aging heat treatment at 725 °C for 3 h increased the strength and hardness of the material. A reinforcement of the cellular microstructure by precipitation of carbides in between the cells is believed to be the main reason for this. To completely alleviate the residual stresses it was necessary to carry out a stress relief annealing process at 950 °C, which resulted in a removal of the cellular structure and a lower strength material.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Aging heat treatment, Austenitic stainless steel, Laser powder bed fusion, Precipitation hardening, Stress relief annealing, Tensile testing
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-103513 (URN)10.1016/j.jmrt.2023.12.063 (DOI)2-s2.0-85179843352 (Scopus ID)
Note

Validerad;2024;Nivå 2;2024-02-26 (joosat);

Full text license: CC BY

Funder: The Swedish National Space Agency; GKN Aerospace Sweden AB;

Available from: 2024-01-08 Created: 2024-01-08 Last updated: 2024-02-26Bibliographically approved
Velarde, L., Nabavi, M. S., Escalera, E., Antti, M.-L. & Akhtar, F. (2023). Adsorption of heavy metals on natural zeolites: A review. Chemosphere, 328, Article ID 138508.
Open this publication in new window or tab >>Adsorption of heavy metals on natural zeolites: A review
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2023 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 328, article id 138508Article, review/survey (Refereed) Published
Abstract [en]

Water pollution has jeopardized human health, and a safe supply of drinking water has been recognized as a worldwide issue. The increase in the accumulation of heavy metals in water from different sources has led to the search for efficient and environmentally friendly treatment methods and materials for their removal. Natural zeolites are promising materials for removing heavy metals from different sources contaminating the water. It is important to know the structure, chemistry, and performance of the removal of heavy metals from water, of the natural zeolites to design water treatment processes. This review focuses on critical analyses of the application of distinct natural zeolites for the adsorption of heavy metals from water, specifically, arsenic (As(III), As(V)), cadmium (Cd(II)), chromium (Cr(III), Cr(VI)), lead (Pb(II)), mercury(Hg(II)) and nickel (Ni(II)). The reported results of heavy-metal removal by natural zeolites are summarized, and the chemical modification of natural zeolites by acid/base/salt reagent, surfactants, and metallic reagents has been analyzed, compared, and described. Furthermore, the adsorption/desorption capacity, systems, operating parameters, isotherms, and kinetics for natural zeolites were described and compared. According to the analysis, clinoptilolite is the most applied natural zeolite to remove heavy metals. It is effective in removing As, Cd, Cr, Pb, Hg, and Ni. Additionally, an interesting fact is a variation between the natural zeolites from different geological origins regarding the sorption properties and capacities for heavy metals suggesting that natural zeolites from different regions of the world are unique.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Adsorption, Heavy metals, Wastewater, Natural zeolites, Clinoptilolite
National Category
Other Earth and Related Environmental Sciences
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-96687 (URN)10.1016/j.chemosphere.2023.138508 (DOI)36972873 (PubMedID)2-s2.0-85151497625 (Scopus ID)
Funder
Sida - Swedish International Development Cooperation Agency, 13486
Note

Validerad;2023;Nivå 2;2023-04-21 (joosat);

Funder: National Natural ScienceFoundation of China (52020105011)

Licens fulltext: CC BY License

Available from: 2023-04-21 Created: 2023-04-21 Last updated: 2023-09-05Bibliographically approved
Sandell, V., Åkerfeldt, P., Hansson, T. & Antti, M.-L. (2023). Fatigue fracture characterization of chemically post-processed electron beam powder bed fusion Ti–6Al–4V. International Journal of Fatigue, 172, Article ID 107673.
Open this publication in new window or tab >>Fatigue fracture characterization of chemically post-processed electron beam powder bed fusion Ti–6Al–4V
2023 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 172, article id 107673Article in journal (Refereed) Published
Abstract [en]

The fatigue behavior of additively manufactured (AM) structural parts is sensitive to the surface and near-surface material conditions. Chemical post-processing surface treatments can be used to improve the surface condition of AM components, including complex geometries with surfaces difficult to access. In this work, surfaces of electron beam powder bed fusion (EB-PBF) produced Ti–6Al–4V were subject to two different chemical post-processing surface treatments, chemical milling and Hirtisation. As-built and machined surfaces, as well as hot isostatic pressing (HIP), treated conditions were also investigated. Fatigue testing was carried out in four-point bending. The investigation focused on the relationship between fracture mechanisms and fatigue life through fractographic study. It was found that a majority of fractures were initiated at internal surface-near defects or defects on the surface. Chemical post-processing was found to smoothen the surface but to leave a surface waviness. Material removal during post-processing could open up internal defects to the treated surface. In HIP-treated specimens, fractures initiated at defects open to the surface. Despite post-processing increasing the mean life of fatigue specimens, no significant improvements in the lowest tested life were observed for any specimen condition.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Electron beam powder bed fusion, Fatigue, Defects, Surface Condition, Fractography, Chemical post-processing
National Category
Other Materials Engineering Manufacturing, Surface and Joining Technology
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-96279 (URN)10.1016/j.ijfatigue.2023.107673 (DOI)2-s2.0-85152121322 (Scopus ID)
Projects
SUDDEN
Funder
Vinnova, 2017-04846
Note

Validerad;2023;Nivå 2;2023-04-17 (hanlid);

Funder: GKN Aerospace Sweden AB

Available from: 2023-03-30 Created: 2023-03-30 Last updated: 2023-09-05Bibliographically approved
Mishra, P., Åkerfeldt, P., Svahn, F., Nilsson, E., Forouzan, F. & Antti, M.-L. (2023). Microstructural characterization and mechanical properties of additively manufactured 21-6-9 stainless steel for aerospace applications. Journal of Materials Research and Technology, 25, 1483-1494
Open this publication in new window or tab >>Microstructural characterization and mechanical properties of additively manufactured 21-6-9 stainless steel for aerospace applications
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2023 (English)In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 25, p. 1483-1494Article in journal (Refereed) Published
Abstract [en]

The alloy 21-6-9 is a nitrogen-strengthened austenitic stainless steel often used in aerospace applications due to its high strength, good fabrication properties, and toughness at cryogenic temperatures. However, minimal research has been conducted on alloy 21-6-9 using the additive manufacturing process laser powder-bed fusion (L-PBF). The L-PBF technique has been seen as a key to reducing production time and avoiding costly machining. Therefore, there is an interest in investigating L-PBF-processed 21-6-9 to determine the effects of L-PBF on properties at elevated and cryogenic temperatures. In this study, prior to tensile testing the alloy 21-6-9 underwent heat treatments that simulated aerospace applications and the alloy was analyzed and characterized to evaluate phase stability. The effects of elevated and cryogenic temperatures (77K) on the tensile behavior and microstructure were investigated using X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The tensile tests showed that the yield strength and ultimate tensile strength improved, while ductility varied depending on the conditions and test environment. The ultimate tensile strength was approximately 80% higher at 77K than at room temperature, although the elongation decreased by around 90%, possibly due to the formation of strain-induced martensite.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
L-PBF, 21-6-9 stainless steel, elevated temperature, cryogenic temperature, microstructural characterization, mechanical properties
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-97925 (URN)10.1016/j.jmrt.2023.06.047 (DOI)2-s2.0-85162113914 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-06-30 (hanlid)

Available from: 2023-06-06 Created: 2023-06-06 Last updated: 2023-09-05Bibliographically approved
Sandell, V., Nilsson, J., Hansson, T., Åkerfeldt, P. & Antti, M.-L. (2022). Effect of chemical post-processing on surfaces and sub-surface defects in electron beam melted Ti-6Al-4V. Materials Characterization, 193, Article ID 112281.
Open this publication in new window or tab >>Effect of chemical post-processing on surfaces and sub-surface defects in electron beam melted Ti-6Al-4V
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2022 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 193, article id 112281Article in journal (Refereed) Published
Abstract [en]

Surfaces after chemical post-processing treatments of electron beam melting (EBM) produced Ti-6Al-4V have been studied. Targeted chemical treatment allowed the study of variation in surface quality with material removal depth. Characterization of surface and defect morphologies were made, comparing two chemical post-processing methods, Hirtisation® and chemical milling with different milling depths. Surface topography was characterized using white light interferometry and subsurface defect distribution was studied using X-ray computed tomography (XCT). The morphology of the surface at different milling depths was compared to the sub-surface information from XCT scans of the as-built material. Furthermore, Hot Isostatic Pressing (HIP) treated material was documented for comparison. Results show that post-processed surfaces contain a number of different defects of mixed morphology, position and origin. Post-processing deteriorates the surface quality with increased removal depth due to the presence of sub-surface defects. The position of sub-surface defects in relation to the material surface coincides with the depth at which contour-hatch interactions are likely to have occurred during the EBM building process. The distribution of this sub-surface defect population is anisotropic in the building (horizontal) plane and reasons for this are explored. Hirtisation® produces surfaces morphologically different from chemically milled surfaces. This difference was found to contribute to Hirtisation® producing surfaces with higher roughness (Sa) than chemically milled surfaces at comparable removal depth. HIP did remove all detectable sub-surface defects but microstructural artefacts indicating healed porosity were found.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Electron beam melting, Chemical post-processing, Defects, X-ray computed tomography, Surface roughness
National Category
Metallurgy and Metallic Materials
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-81153 (URN)10.1016/j.matchar.2022.112281 (DOI)000862845800001 ()2-s2.0-85138088971 (Scopus ID)
Projects
SUDDEN
Funder
Vinnova, 2017–04846
Note

Validerad;2022;Nivå 2;2022-09-26 (joosat);

Funder: GKN Aerospace Sweden AB

This article has previously appeared as a manuscript in a thesis.

Available from: 2020-10-15 Created: 2020-10-15 Last updated: 2023-09-05Bibliographically approved
Mishra, P., Åkerfeldt, P. & Antti, M.-L. (2022). Effect of hatch distance on the microestructure and mechanical properties of 316 L built by the L-PBF process. In: : . Paper presented at 11th EEIGM International Conference on Advanced Materials Research, June 16-17, 2022, Barcelona, Spain.
Open this publication in new window or tab >>Effect of hatch distance on the microestructure and mechanical properties of 316 L built by the L-PBF process
2022 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

The laser powder bed fusion (L-PBF) process is an additive manufacturing (AM) process of building parts that uses the high power of the laser to melt the fine powder bed and form a structure, as shown in figure 1 (a). As a result, L-PBF is a promising technique that has likely demonstrated great interest in producing a complex part with near-net-shape design in the area of high-performance applications [1-4]. However, the defects formed during the manufacturing process affect the mechanical properties of a component, as seen in Figure 1 (b). Therefore, track remelting is required to avoid defects and thus low process efficiency [4], as shown in Figure 1 (c). In this study, five different hatch distances of 20 µm, 50 µm, 80 µm, 110 µm, and 140 µm of 316 L stainless steel were studied. To understand the effect of different hatch distances on microstructure, including crystallographic orientation and hardness, EBSD and nanoindentation hardness techniques are used. In addition, the porosity formed is calculated and distinguished (different defects, such as lack of fusion, gas pores, and keyhole defects) using image analysis software MIPAR.(a)(b)(c) Figure 1:(a) Arrangement of the building of tracks and layers during the L-PBF process,(b) illustration of cavity formation, and (c) various times of remelting while building a new build track [4].

National Category
Manufacturing, Surface and Joining Technology
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-97924 (URN)
Conference
11th EEIGM International Conference on Advanced Materials Research, June 16-17, 2022, Barcelona, Spain
Available from: 2023-06-06 Created: 2023-06-06 Last updated: 2023-09-05Bibliographically approved
Torkamani, H., Vivas Méndez, J., Lecart, C., Aldanondo Begiristain, E., Alvarez Moro, P. & Antti, M.-L. (2022). Effect of Rotation Speed and Steel Microstructure on Joint Formation in Friction Stir Spot Welding of Al Alloy to DP Steel. Journal of Manufacturing and Materials Processing, 6(1), Article ID 24.
Open this publication in new window or tab >>Effect of Rotation Speed and Steel Microstructure on Joint Formation in Friction Stir Spot Welding of Al Alloy to DP Steel
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2022 (English)In: Journal of Manufacturing and Materials Processing, E-ISSN 2504-4494, Vol. 6, no 1, article id 24Article in journal (Refereed) Published
Abstract [en]

In this work, friction stir spot welding of 5754 aluminum alloy to dual phase steel was investigated using two different ratios of martensite and ferrite (0.38 and 0.61) for steel sheet initial microstructure and varying tool rotation speed (800, 1200 and 2000 rpm). The effect of these parameters on the joint formation was evaluated by studying the plunging force response during the process and the main characteristics of the joint at (i) macrolevel, i.e., hook morphology and bond width, and (ii) microlevel, i.e., steel hook and sheet microstructure and intermetallic compounds. The plunging force was reduced by increased tool rotation speed while there was no significant effect from the initial steel microstructure ratio of martensite and ferrite on the plunging force. The macrostructural characterization of the joints showed that the hook morphology and bond width were affected by the steel sheet initial microstructures as well as by the tool rotation speed and by the material flow driver; tool pin or shoulder. At microstructural level, a progressive variation in the ratio of martensite and ferrite was observed for the steel hook and sheet microstructure. The zones closer to the tool presented a fully martensitic microstructure while the zones away from the tool showed a gradual increase in the ferrite amount until reaching the ratio of ferrite and martensite of the steel sheet initial microstructure. Different types of FexAly intermetallic compounds were found in three zones of the joint; the hook tips, in the hooks close to the exit hole and in the corner of the exit hole. These compounds were characterized by a brittle behavior with hardness values varying from 456 to 937 HV01.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
friction stir spot welding, material flow, dissimilar, dual-phase steel, hook characteristic, intermetallic compounds
National Category
Manufacturing, Surface and Joining Technology
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-89590 (URN)10.3390/jmmp6010024 (DOI)000769721800001 ()2-s2.0-85124879726 (Scopus ID)
Note

Validerad;2022;Nivå 2;2022-03-14 (johcin)

Available from: 2022-03-14 Created: 2022-03-14 Last updated: 2023-09-05Bibliographically approved
Torkamani, H., Vrček, A., Larsson, R. & Antti, M.-L. (2022). Micro-pitting and wear damage characterization of through hardened 100Cr6 and surface induction hardened C56E2 bearing steels. Wear, 492-493, Article ID 204218.
Open this publication in new window or tab >>Micro-pitting and wear damage characterization of through hardened 100Cr6 and surface induction hardened C56E2 bearing steels
2022 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 492-493, article id 204218Article in journal (Refereed) Published
Abstract [en]

Rolling-sliding contact fatigue experiments were performed on through hardened (TH) 100Cr6 and surface induction hardened (SIH) C56E2 bearing steels to study the effect of heat treatment procedure and hardness difference on their wear and/or surface-initiated damage. The heat-treated microstructures included tempered martensite without the presence of retained austenite. It was found that initial stress distribution below the surface of TH specimens remains close to zero with respect to the depth, while, employing SIH resulted in relatively high compressive residual stresses. The wear damage of the specimens was characterized for negative ΔH (i.e., specimen's hardness minus counterpart's hardness) subjected to rolling-sliding contact in a twin-disc configuration operated under a mixed lubrication condition. According to the wear mechanisms and damages assessed, three regions were distinguished: i) mild wear and onset of micropitting, ii) transition region from mild to severe micro-pitting and iii) severe micro-pitting wear. Decreasing the ΔH resulted in a gradual increase in the wear rate of TH specimens, while, the increase in the wear rate of SIH specimens was delayed; with a same absolute hardness, TH specimen with a ΔH of −84 HV already reached the third wear region, while a SIH specimen with a ΔH of −150 HV still operates in the second region. Inspection of the affected subsurface unveiled the response of worn microstructures to the etchant and how the micro-cracks could possibly form within the wear affected zone. The results obtained were mainly explained based on the state of the residual stresses, possible contributions of the microstructural features, and wear behavior (material removal) of the specimen.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Rolling-sliding, Contact fatigue, Hardness difference, Residual stress, micro-pitting
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-88620 (URN)10.1016/j.wear.2021.204218 (DOI)000754309900002 ()2-s2.0-85121831976 (Scopus ID)
Funder
The Kempe FoundationsSwedish Energy Agency, P41215-1
Note

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Available from: 2021-12-30 Created: 2021-12-30 Last updated: 2023-09-05Bibliographically approved
Edin, E., Svahn, F., Åkerfeldt, P., Eriksson, M. & Antti, M.-L. (2022). Rapid method for comparative studies on stress relief heat treatment of additively manufactured 316L. Materials Science & Engineering: A, 847, Article ID 143313.
Open this publication in new window or tab >>Rapid method for comparative studies on stress relief heat treatment of additively manufactured 316L
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2022 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 847, article id 143313Article in journal (Refereed) Published
Abstract [en]

The additive manufacturing method laser powder bed fusion (L-PBF) is known to introduce large residual stresses in the built component. Optimization of process parameters and subsequent heat treatment is crucial to relieve these residual stresses. However, many of the available tools used to analyze these residual stresses are either prohibitively expensive, or too time consuming for initial prototyping stages.

A qualitative method for rapid evaluation of the effectiveness of stress relief heat treatment of L-PBF manufactured 316L has been tested. Residual stress induced distortion has been measured with contact and non-contact methods to study the effect of different stress relief heat treatment temperatures (600 – 950 °C, fixed holding time: 1 h). Over the examined temperature interval, at which deformation was measured, distinct differences were observable at each temperature with both methods. Based on the distortion, shape stability was considered reached after subjecting the test geometry to a heat treatment temperature of 900 °C for 1 hour. Complementary mechanical testing and microstructural characterization were carried out to provide a more general understanding of the implications of each heat treatment temperature. Microstructural characterization revealed that complete dissolution of the cellular sub-grain features occurred at the same temperature as where the minimum magnitude of distortion was obtained.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Laser powder bed fusion, stainless steel, residual stress, mechanical properties, heat treatment
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-90614 (URN)10.1016/j.msea.2022.143313 (DOI)000841176900004 ()2-s2.0-85134070846 (Scopus ID)
Funder
European Regional Development Fund (ERDF)
Note

Validerad;2022;Nivå 2;2022-05-31 (joosat);

Funder: Swedish National Space Agency (NRFP4: 71/19); GKN Aerospace Sweden AB

Available from: 2022-05-12 Created: 2022-05-12 Last updated: 2023-09-05Bibliographically approved
Sandell, V., Hansson, T., Roychowdhury, S., Månsson, T., Delin, M., Åkerfeldt, P. & Antti, M.-L. (2021). Defects in Electron Beam Melted Ti-6Al-4V: Fatigue Life Prediction Using Experimental Data and Extreme Value Statistics. Materials, 14(3), Article ID 640.
Open this publication in new window or tab >>Defects in Electron Beam Melted Ti-6Al-4V: Fatigue Life Prediction Using Experimental Data and Extreme Value Statistics
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2021 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 14, no 3, article id 640Article in journal (Refereed) Published
Abstract [en]

Electron beam melting is a powder bed fusion (PBF) additive manufacturing (AM) method for metals offering opportunities for the reduction of material waste and freedom of design, but unfortunately also suffering from material defects from production. The stochastic nature of defect formation leads to a scatter in the fatigue performance of the material, preventing wider use of this production method for fatigue critical components. In this work, fatigue test data from electron beam melted Ti-6Al-4V specimens machined from as-built material are compared to deterministic fatigue crack growth calculations and probabilistically modeled fatigue life. X-ray computed tomography (XCT) data evaluated using extreme value statistics are used as the model input. Results show that the probabilistic model is able to provide a good conservative life estimate, as well as accurate predictive scatter bands. It is also shown that the use of XCT-data as the model input is feasible, requiring little investigated material volume for model calibration.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
additive manufacturing, electron beam melting, Ti-6Al-4V, defects, fatigue life, fracture mechanics, fatigue crack propagation, probabilistic modeling
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-81154 (URN)10.3390/ma14030640 (DOI)000615396300001 ()33573246 (PubMedID)2-s2.0-85100309316 (Scopus ID)
Projects
SUDDEN
Funder
Vinnova, 2017-04846
Note

Validerad;2021;Nivå 2;2021-02-16 (alebob);

Artikeln har tidigare förekommit som manuskript i avhandling

Available from: 2020-10-15 Created: 2020-10-15 Last updated: 2023-09-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3661-9262

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