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Publications (10 of 72) Show all publications
Lupi, G., de Menezes, J. T., Belelli, F., Bruzzo, F., Volpp, J., Castrodeza, E. M. & Casati, R. (2023). Fracture Toughness And Fatigue Properties Of Alsi10mg Alloy Produced By Direct Energy Deposition With Different Crack Plane Orientations. In: Euro Powder Metallurgy 2023 (Euro PM2023) Proceedings: . Paper presented at Euro Powder Metallurgy 2023 Congress and Exhibition (Euro PM2023), Lisbon, Portugal, October 1-4, 2023. European Powder Metallurgy Association (EPMA)
Open this publication in new window or tab >>Fracture Toughness And Fatigue Properties Of Alsi10mg Alloy Produced By Direct Energy Deposition With Different Crack Plane Orientations
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2023 (English)In: Euro Powder Metallurgy 2023 (Euro PM2023) Proceedings, European Powder Metallurgy Association (EPMA) , 2023Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
European Powder Metallurgy Association (EPMA), 2023
National Category
Metallurgy and Metallic Materials Applied Mechanics
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-103428 (URN)10.59499/EP235765625 (DOI)2-s2.0-85180373266 (Scopus ID)
Conference
Euro Powder Metallurgy 2023 Congress and Exhibition (Euro PM2023), Lisbon, Portugal, October 1-4, 2023
Available from: 2024-01-02 Created: 2024-01-02 Last updated: 2024-01-02Bibliographically approved
Lupi, G., de Menezes, J. T., Belelli, F., Bruzzo, F., López, E., Volpp, J., . . . Casati, R. (2023). Fracture toughness of AlSi10Mg alloy produced by direct energy deposition with different crack plane orientations. Materials Today Communications, 37, Article ID 107460.
Open this publication in new window or tab >>Fracture toughness of AlSi10Mg alloy produced by direct energy deposition with different crack plane orientations
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2023 (English)In: Materials Today Communications, ISSN 2352-4928, Vol. 37, article id 107460Article in journal (Refereed) Published
Abstract [en]

Three-point bending fracture toughness and tensile specimens were tested at room temperature along different crack plane orientations and loading directions. Before being machined and tested, the printed samples were subjected to heat treatment at 300 °C for 2 h to relieve the residual stresses. Microstructural and fractographic analyses were performed to investigate the fracture mechanisms and the crack propagation paths for each crack orientation. Significant differences in the fracture toughness were observed among the crack plane orientations. Specimens with cracks oriented in the X-Y direction featured the highest fracture toughness values (JIc = 11.96 kJ/m2), whereas the Z-Y crack orientation (perpendicular to the printing direction) performed the lowest fracture toughness values (JIc = 8.91 kJ/m2). The anisotropy in fracture toughness is mainly related to a preferential crack propagation path along the melt pool boundaries. At melt pool boundaries, pores are preferentially placed, coarsening of the microstructure occurs and there is higher Si content, leading to that area being less ductile and less resistant to crack propagation.

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
AlSi10Mg alloy, Direct energy deposition, Fracture toughness, J-R curves, Tensile properties, Toughness anisotropy
National Category
Applied Mechanics
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-102320 (URN)10.1016/j.mtcomm.2023.107460 (DOI)2-s2.0-85175349557 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-11-14 (marisr);

Funder: EIT (18079);

License fulltext: CC BY-NC-ND

Available from: 2023-11-06 Created: 2023-11-06 Last updated: 2023-11-14Bibliographically approved
Faue, P., Rathmann, L., Möller, M., Hassan, M., Clark, S. J., Fezzaa, K., . . . Pfefferkorn, F. E. (2023). High-speed X-ray study of process dynamics caused by surface features during continuous-wave laser polishing. CIRP annals, 72(1), 201-204
Open this publication in new window or tab >>High-speed X-ray study of process dynamics caused by surface features during continuous-wave laser polishing
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2023 (English)In: CIRP annals, ISSN 0007-8506, E-ISSN 1726-0604, Vol. 72, no 1, p. 201-204Article in journal (Refereed) Published
Abstract [en]

During high-speed X-ray imaging of laser surface polishing experiments of specimens of 316L stainless steel at Argonne National Lab's Advanced Photon Source, it was discovered that the induced keyhole changes shape and dimensions while crossing an engineered surface feature without altering process parameters. It was observed that the post-surface feature keyhole was deeper than that of the pre surface feature keyhole. This work reports on the first in-situ observation of the effect of localized surface geometry on underlying melt pool behavior. This has implications for defect formation mechanisms during laser melting processes that rely on melt pool geometry.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Laser, Polishing, X-ray imaging
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-97018 (URN)10.1016/j.cirp.2023.04.026 (DOI)2-s2.0-85152666479 (Scopus ID)
Funder
Swedish Research Council, 2020-04250
Note

Validerad;2023;Nivå 2;2023-08-16 (marisr);

Funder: National Science Foundation (CMMI-1727366); Deutsche Forschungsgemeinschaft (386371584)

Available from: 2023-05-05 Created: 2023-05-05 Last updated: 2023-08-16Bibliographically approved
Volpp, J. (2023). High-temperature laser absorption of steel. In: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023: . Paper presented at 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Munich, Germany, June 26-30, 2023. Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>High-temperature laser absorption of steel
2023 (English)In: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Institute of Electrical and Electronics Engineers Inc. , 2023Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2023
Series
Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference, ISSN 2639-5452, E-ISSN 2833-1052
National Category
Atom and Molecular Physics and Optics
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-103527 (URN)10.1109/CLEO/EUROPE-EQEC57999.2023.10231986 (DOI)2-s2.0-85175707994 (Scopus ID)979-8-3503-4599-5 (ISBN)979-8-3503-4600-8 (ISBN)
Conference
2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Munich, Germany, June 26-30, 2023
Available from: 2024-01-10 Created: 2024-01-10 Last updated: 2024-02-09Bibliographically approved
Volpp, J. (2023). Impact of Melt Flow and Surface Tension on Gap Bridging During Laser Beam Welding. Lasers in Manufacturing and Materials Processing
Open this publication in new window or tab >>Impact of Melt Flow and Surface Tension on Gap Bridging During Laser Beam Welding
2023 (English)In: Lasers in Manufacturing and Materials Processing, ISSN 2196-7229Article in journal (Refereed) Epub ahead of print
Abstract [en]

Laser beam welding is an essential technology to enable the transformation to enforce e-mobility. When manufacturing light weight structures like the chassis, precision, speed, quality and low deformation can be expected when using the laser beam as a welding heat source. However, the laser beam is typically used at small dimensions and can fail to transfer its energy to the joining partners when the gap between them becomes large. Beam shaping technologies have developed in the last years to be flexibly used for high-power processes and provide an opportunity to alter the energy input and thereby improve the welding quality and gap bridgability. In this work, multi-spot beam shaping was analyzed using up to nine spots. Experiments were performed using different beam shapes in order to redistribute the energy input, recording the process using high-speed imaging for detection of melt pool dimensions. Those were used as input for a simplified analytical model predicting the process collapse based on the available melt material. Several beam shapes created melt pools that support the material availability behind the keyhole(s). Numerical simulations showed that directed melt flows induced by the keyhole(s) can increase the gap bridgability.

Place, publisher, year, edition, pages
Springer, 2023
Keywords
Fluid Flow, Gap Bridging, Keyhole Welding, Modelling, Simulation
National Category
Manufacturing, Surface and Joining Technology Other Mechanical Engineering
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-99267 (URN)10.1007/s40516-023-00222-9 (DOI)2-s2.0-85165887356 (Scopus ID)
Funder
Swedish Research Council, 2020–04250
Note

Funding: EC Research Fund for Coaland Steel, RFCS, (800726)

Licens fulltext: CC BY License

Available from: 2023-08-07 Created: 2023-08-07 Last updated: 2023-08-07
Volpp, J. (2023). Laser beam absorption measurement at molten metal surfaces. Measurement, 209, Article ID 112524.
Open this publication in new window or tab >>Laser beam absorption measurement at molten metal surfaces
2023 (English)In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 209, article id 112524Article in journal (Refereed) Published
Abstract [en]

Laser light absorption is one of the elementary effects of laser material processing. Absorption values are relevant to calculate the process efficiency and predict the impact on the material for the increasingly used laser processes. However, absorption measurement can be a complex task. At high temperatures of metals, only limited experimental data is available due to the dynamic surfaces and the often unknown emissivity needed for the temperature measurement. Models were created to predict the absorption at different temperatures, which are successful with assumptions in some regimes, but often fail in others. For improving the theoretical models, an experimental measurement of high-temperature metal surfaces is desired. Therefore, a radiometric measurement method is proposed in this work using a heating laser to create a metal melt pool, while measuring temperature and reflection of its surface by a second measuring laser beam. General tendencies known from literature could be confirmed by the measurements, while absorption values tend to scatter at increasing temperature. However, trends could be observed. Between melting and boiling temperature, a slight absorption increase was seen in the range between 35% and 38%. Those values indicate that both interband and intraband absorption must be considered to explain the absorption in this regime. At increased temperatures, the intraband absorption becomes the dominating absorption mechanism, reaching absorption values above 45% at very high temperatures.

Place, publisher, year, edition, pages
Elsevier B.V., 2023
Keywords
Absorptivity, Boiling temperature, Infrared laser, Melting temperature, Reflectivity
National Category
Atom and Molecular Physics and Optics
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-95608 (URN)10.1016/j.measurement.2023.112524 (DOI)2-s2.0-85147252034 (Scopus ID)
Funder
Swedish Research Council, (2020-04250)
Note

Validerad;2023;Nivå 2;2023-02-13 (joosat);

Funder: EIT raw materials, (18079)

Licens fulltext: CC BY License

Available from: 2023-02-13 Created: 2023-02-13 Last updated: 2023-02-13Bibliographically approved
Volpp, J. (2023). Laser light absorption and Brewster angle on liquid metal. Journal of Applied Physics, 133(20), Article ID 205902.
Open this publication in new window or tab >>Laser light absorption and Brewster angle on liquid metal
2023 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 133, no 20, article id 205902Article in journal (Refereed) Published
Abstract [en]

Laser light absorption occurs in all laser-based processes and is, therefore, of importance for process simulation input, parameter optimization, and understanding of the occurring phenomena, such as melt pool flow or vaporization effects. Theoretical models were successful in predicting metal absorption for certain cases but often fail in high-temperature situations due to unknown impacts of occurring effects, such as surface irregularities or contaminations. Measuring absorption at high temperatures is challenging, and there are limited literature data available on values further above melting temperatures of metals. In this work, a radiometric measurement method is used to derive absorption values at high temperatures. The results show shifted values from Fresnel predictions and absorption peaks at comparably low incident angles. The decreasing absorption tendency at low incident angles was shown to be possibly induced by multi-interface absorption effects caused by surface layering and Knudsen layer effects. Surface layering was seen to be able to induce a very low Brewster angle comparable to the observations in the measurements and is, therefore, seen as a possible dominant factor in absorption at elevated temperatures.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2023
National Category
Energy Engineering
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-98588 (URN)10.1063/5.0146728 (DOI)2-s2.0-85161020631 (Scopus ID)
Funder
Swedish Research Council, 2020-04250 SMART
Note

Validerad;2023;Nivå 2;2023-06-19 (hanlid)

Available from: 2023-06-19 Created: 2023-06-19 Last updated: 2023-06-19Bibliographically approved
Volpp, J. (2023). Laser light absorption of high-temperature metal surfaces. Heliyon, 9(10), Article ID e21021.
Open this publication in new window or tab >>Laser light absorption of high-temperature metal surfaces
2023 (English)In: Heliyon, E-ISSN 2405-8440, Vol. 9, no 10, article id e21021Article in journal (Refereed) Published
Abstract [en]

Laser beam absorption is the basic effect to enable many high-temperature applications and processes. However, high temperature absorption data of metals is often not available or based on theoretical assumptions. In this work, using a newly developed experimental arrangement to measure laser light absorption on liquid metal surfaces even above boiling temperature enabled the derivation of absorption values in those regimes. Results indicate that interband absorption must be considered even at such high temperatures against common theoretical predictions. It is shown that the simulated nearly constant absorption depth and absorption values between melting and boiling temperatures indicate that the increased atom distance due to thermal expansion, denoting a reduced absorption volume, is counterbalanced by the increased statistical availability of conduction electrons due to Fermi band broadening.

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Laser light absorption, Laser treatment, Molecular dynamics
National Category
Atom and Molecular Physics and Optics
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-101974 (URN)10.1016/j.heliyon.2023.e21021 (DOI)2-s2.0-85174209017 (Scopus ID)
Funder
Swedish Research Council
Note

Validerad;2023;Nivå 2;2023-11-08 (marisr);

License fulltext: CC BY

Available from: 2023-10-31 Created: 2023-10-31 Last updated: 2023-11-08Bibliographically approved
Volpp, J. (2023). Surface tension of steel at high temperatures. SN Applied Sciences, 5(9), Article ID 237.
Open this publication in new window or tab >>Surface tension of steel at high temperatures
2023 (English)In: SN Applied Sciences, ISSN 2523-3963, E-ISSN 2523-3971, Vol. 5, no 9, article id 237Article in journal (Refereed) Published
Abstract [en]

Surface tension is a material property that is needed to describe fluid behaviour, which impacts industrial processes, in which molten material is created, such as thermal cutting, welding and Additive Manufacturing. In particular when using metals, the material properties at high temperatures are often not known. This is partly because of limited possibilities to measure those properties, limitations of temperature measurement methods and a lack of theoretical models that describe the circumstances at such high temperatures sufficiently. When using beam heat sources, such as a laser beam, temperatures far above the melting temperature are reached. Therefore, it is mandatory to know the material properties at such high temperatures in order to describe the material behaviour in models and gain understanding of the occurring effects. Therefore, in this work, an experimental surface wave evaluation method is suggested in combination with thermal measurements in order to derive surface tension values of steel at higher temperatures than reported in literature. The evaluation of gravity-capillary waves in high-speed video recordings shows a steeper decrease of surface tension values than the extrapolation of literature values would predict, while the surface tension values seem not to decrease further above boiling temperature. Using a simplified molecular dynamic model based on pair correlation, a similar tendency of surface values was observed, which indicates that the surface tension is an effect requiring at least two atomic layers. The observed and calculated decreasing trend of the surface tension indicates an exponential relation between surface tension and temperature.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
Boiling temperature, Laser processing, Surface tension
National Category
Other Materials Engineering
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-101205 (URN)10.1007/s42452-023-05456-y (DOI)001048586700002 ()2-s2.0-85168308049 (Scopus ID)
Funder
Swedish Research Council, 2020-04250
Note

Validerad;2023;Nivå 2;2023-09-05 (joosat);

CC BY 4.0 License

Available from: 2023-09-05 Created: 2023-09-05 Last updated: 2023-09-05Bibliographically approved
Hauser, T., Reisch, R. T., Kamps, T., Kaplan, A. F. .. & Volpp, J. (2022). Acoustic emissions in directed energy deposition processes. The International Journal of Advanced Manufacturing Technology, 119(5-6), 3517-3532
Open this publication in new window or tab >>Acoustic emissions in directed energy deposition processes
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2022 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 119, no 5-6, p. 3517-3532Article in journal (Refereed) Published
Abstract [en]

Acoustic emissions in directed energy deposition processes such as wire arc additive manufacturing and directed energy deposition with laser beam/metal are investigated within this work, as many insights about the process can be gained from this. In both processes, experienced operators can hear whether a process is running stable or not. Therefore, different experiments for stable and unstable processes with common process anomalies were carried out, and the acoustic emissions as well as process camera images were captured. Thereby, it was found that stable processes show a consistent mean intensity in the acoustic emissions for both processes. For wire arc additive manufacturing, it was found that by the Mel spectrum, a specific spectrum adapted to human hearing, the occurrence of different process anomalies can be detected. The main acoustic source in wire arc additive manufacturing is the plasma expansion of the arc. The acoustic emissions and the occurring process anomalies are mainly correlating with the size of the arc because that is essentially the ionized volume leading to the air pressure which causes the acoustic emissions. For directed energy deposition with laser beam/metal, it was found that by the Mel spectrum, the occurrence of an unstable process can also be detected. The main acoustic emissions are created by the interaction between the powder and the laser beam because the powder particles create an air pressure through the expansion of the particles from the solid state to the liquid state when these particles are melted. These findings can be used to achieve an in situ quality assurance by an in-process analysis of the acoustic emissions.

Place, publisher, year, edition, pages
Springer, 2022
Keywords
Wire arc additive manufacturing, Laser metal deposition, WAAM, LMD, In situ monitoring, Airborne acoustic emissions
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-88283 (URN)10.1007/s00170-021-08598-8 (DOI)000740196700001 ()2-s2.0-85122527372 (Scopus ID)
Funder
Swedish Research Council, 2020–04250
Note

Validerad;2022;Nivå 2;2022-03-10 (hanlid);

Funder: BayVFP (IUK-1905–0013); EIT RawMaterials (18079);

Artikeln har tidigare förekommit som manuskript i avhandling

Available from: 2021-12-10 Created: 2021-12-10 Last updated: 2022-07-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-0194-9018

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