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Tamil Alagan, N., Zeman, P., Mara, V., Beno, T. & Wretland, A. (2021). High-pressure flank cooling and chip morphology in turning Alloy 718. CIRP - Journal of Manufacturing Science and Technology, 35, 659-674
Open this publication in new window or tab >>High-pressure flank cooling and chip morphology in turning Alloy 718
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2021 (English)In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 35, p. 659-674Article in journal (Refereed) Published
Abstract [en]

The use of cutting fluids is commonly considered a necessity while machining Heat Resistant Super Alloys (HRSA). Specifically, cutting fluids applied under high-pressure, which for many decades have been the solution for the most demanding applications. The results might be diverse and vary between applications, but typically leads to improved tool life, enhanced chip breakability, lower temperature in the cutting zone and better surface quality of the finished product. The available high-pressure cutting fluid delivery systems are usually designed with the intention to improve the cutting fluid penetration at the vicinity of the cutting edge on the rake face side of the insert. However, there has been limited interest in investigating high-pressure cutting fluid applied to its flank face. Both specifically and in combination with cutting fluid directed to the rake face. In this study, the focus has been to investigate the chip formation process during the turning of Alloy 718 (Inconel 718). Particularly, for a defined turning operation where high-pressure cutting fluid is applied to the flank side as well as the rake side of an uncoated carbide insert. Several combinations of pressure levels and jet directions were investigated. The corresponding effects on the tool-chip contact zone and chip characteristics were studied for two cutting speeds. The results of the investigation showed a substantial improvement in lowering the tool-chip contact area at a rake pressure of 16 MPa. At which pressure, additional cutting fluid applied to the flank at a moderate pressure of 8 MPa had no dominant effect on chip formation (chip break). However, flank cooling of the cutting zone supports chip segmentation and thus indirectly chip breakability. For cutting fluid applied to the rake side at a more moderate pressure of 8 MPa, more prominent effects on the insert became apparent when additional cutting fluid was applied to the flank side. This was particularly noticeable when cutting fluid was directed towards the flank side of the insert at the same pressure level as the cutting fluid applied towards its rake face. The additional thermal transfer was seen to have a significant effect on the material deformation phenomena in the primary shear zone (lowering shear angle) as well as the sliding and sticking conditions of the tool-chip interface. Based on the evidence from this study, it can be concluded that cutting fluid applied towards the flank side of the insert has a significant impact on the cutting process. In particular, if applied in combination with a rake pressure at a similar level, in this case, 8 MPa. © 2021 The Authors

Place, publisher, year, edition, pages
Elsevier Ltd, 2021
Keywords
Carbide cutting tools; Carbides; Cutting; Cutting fluids; Morphology; Shear flow; Thermal management (electronics); Turning, Chip segmentation; Lower temperatures; Material deformation; Moderate pressures; Tool-chip contact; Tool-chip contact area; Tool-chip interface; Turning operations, Cutting tools
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17512 (URN)10.1016/j.cirpj.2021.08.012 (DOI)000704828400002 ()2-s2.0-85115002466 (Scopus ID)
Funder
Region Västra Götaland
Note

The authors would like to thank both the national funding organizations/projects, Sweden: Västra Götalands Regionen (VGR), PROSAM project (Dnr RUN 612-0974-13) and Czech Republic: This work was supported by the project Novel nanostructures for engineering applications No. CZ.02.1.01/0.0/0.016 026/0008396. We would also like to thank Sandvik Coromant for the support with inserts. A special thanks goes to Andreas Gustafsson at University West and Andreas Lindberg at GKN Aerospace Engine Systems AB for helping with experiments. Sauruck Clemens, Bruker Alicona, Austria in helping with the license of 3-D measurement software.

Available from: 2021-09-30 Created: 2021-09-30 Last updated: 2022-01-20
Parsian, A., Eynian, M., Magnevall, M. & Beno, T. (2021). Minimizing the Negative Effects of Coolant Channels on the Torsional and Torsional-Axial Stiffness of Drills. Metals, 11(9)
Open this publication in new window or tab >>Minimizing the Negative Effects of Coolant Channels on the Torsional and Torsional-Axial Stiffness of Drills
2021 (English)In: Metals, ISSN 2075-4701, Vol. 11, no 9Article in journal (Refereed) Published
Abstract [en]

Coolant channels allow internal coolant delivery to the cutting region and significantly improve drilling, but these channels also reduce the torsional and torsional-axial stiffness of the drills. Such a reduction in stiffness can degrade the quality of the drilled holes. The evacuation of cutting chips and the delivery of the cutting fluid put strict geometrical restrictions on the cross-section design of the drill. This necessitates careful selection and optimization of features such as the geometry of the coolant channels. This paper presents a new method that uses Prandtl's stress function to predict the torsional and torsional-axial stiffness values. Using this method drills with one central channel are compared to those with two eccentric coolant channels, which shows that with the same cross-section area, the reduction of axial and torsional-axial stiffness is notably smaller for the design with two eccentric channels compared to a single central channel. The stress function method is further used to select the appropriate location of the eccentric coolant channels to minimize the loss of torsional and torsional-axial stiffness. These results are verified by comparison to the results of three-dimensional finite element analyses.

Keywords
drilling; dynamics; stress function; torsional stiffness; torsional-axial stiffness
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17507 (URN)10.3390/met11091473 (DOI)000701398500001 ()
Note

This research was funded by “Stiftelsen för Kunskaps- och Kompetensutveckling” and Sandvik Coromant. Further support from the Research School of Simulation and Control of Materialaffecting Processes (SiCoMaP) at University West, Sweden is greatly appreciated.

Available from: 2021-09-30 Created: 2021-09-30 Last updated: 2022-03-31
Holmberg, J., Wretland, A., Berglund, J., Beno, T. & Karlsson, A. M. (2021). Surface Integrity Investigation to Determine Rough Milling Effects for Assessment of Machining Allowance for Subsequent Finish Milling of Alloy 718. Journal of manufacturing and materials processing, 5(2)
Open this publication in new window or tab >>Surface Integrity Investigation to Determine Rough Milling Effects for Assessment of Machining Allowance for Subsequent Finish Milling of Alloy 718
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2021 (English)In: Journal of manufacturing and materials processing, E-ISSN 2504-4494, Vol. 5, no 2Article in journal (Refereed) Published
Abstract [en]

The planned material volume to be removed from a blank to create the final shape of a part is commonly referred to as allowance. Determination of machining allowance is essential and has a great impact on productivity. The objective of the present work is to use a case study to investigate how a prior rough milling operation affects the finish machined surface and, after that, to use this knowledge to design a methodology for how to assess the machining allowance for subsequent milling operations based on residual stresses. Subsequent milling operations were performed to study the final surface integrity across a milled slot. This was done by rough ceramic milling followed by finish milling in seven subsequent steps. The results show that the up-, centre and down-milling induce different stresses and impact depths. Employing the developed methodology, the depth where the directional influence of the milling process diminishes has been shown to be a suitable minimum limit for the allowance. At this depth, the plastic flow causing severe deformation is not present anymore. It was shown that the centre of the milled slot has the deepest impact depth of 500 mu m, up-milling caused an intermediate impact depth of 400 mu m followed by down milling with an impact depth of 300 mu m. With merged envelope profiles, it was shown that the effects from rough ceramic milling are gone after 3 finish milling passes, with a total depth of cut of 150 mu m.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
high volumetric milling; material removal rate; machining allowance determination; alloy 718; surface integrity; residual stresses
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17257 (URN)10.3390/jmmp5020048 (DOI)000668154600001 ()2-s2.0-85106944788 (Scopus ID)
Funder
Vinnova, 2018-02976
Available from: 2021-11-09 Created: 2021-11-09 Last updated: 2021-11-09
Holmberg, J., Wretland, A., Hammersberg, P., Berglund, J., Suarez, A. & Beno, T. (2021). Surface integrity investigations for prediction of fatigue properties after machining of alloy 718. International Journal of Fatigue, 144, Article ID 106059.
Open this publication in new window or tab >>Surface integrity investigations for prediction of fatigue properties after machining of alloy 718
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2021 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 144, article id 106059Article in journal (Refereed) Published
Abstract [en]

Fatigue performance is crucial for gas turbine components, and it is greatly affected by the manufacturing processes. Ability to predict the expected fatigue life of a component based on surface integrity has been the objective in this work, enabling new processing methods. Alloy 718 samples were prepared by different machining setups, evaluated in fatigue testing and surface integrity investigations. These results generated two predictive statistical multi-variate regression models. The fatigue correlated well with roughness, residual stresses and deformation. The two models showed great potential, which encourages further exploration to fine-tune the procedure for the particular case.

Keywords
Surface integrity; Fatigue prediction; Alloy 718; Machining; Non-conventional machining
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17282 (URN)10.1016/j.ijfatigue.2020.106059 (DOI)000606749400005 ()2-s2.0-85097719719 (Scopus ID)
Available from: 2021-10-01 Created: 2021-10-01 Last updated: 2022-03-30
Holmberg, J., Wretland, A., Berglund, J. & Beno, T. (2020). A detailed investigation of residual stresses after milling Inconel 718 using typical production parameters for assessment of affected depth. Materials Today Communications, 24, Article ID 100958.
Open this publication in new window or tab >>A detailed investigation of residual stresses after milling Inconel 718 using typical production parameters for assessment of affected depth
2020 (English)In: Materials Today Communications, ISSN 2352-4928, Vol. 24, article id 100958Article in journal (Refereed) Published
Abstract [en]

Production of superalloy gas turbine parts involves time consuming milling operations typically performed in a sequence from rough to finish milling. Rough milling using ceramic inserts allows high removal rates but causes severe sub-surface impact. A relatively large allowance is therefore left for subsequent cemented carbide milling. With increased knowledge of the affected depth it will be possible to reduce the machining allowance and increase efficiency of the manufacturing process. Milling Inconel 718 using typical production parameters has been investigated using new and worn ceramic and cemented carbide inserts. Residual stresses in a milled slot were measured by x-ray diffraction. Stresses were measured laterally across the slot and below the surface, to study the depth affected by milling. The most important result from this work is the development of a framework concerning how to evaluate the affected depth for a milling operation. The evaluation of a single milled slot shows great potential for determining the optimum allowance for machining. Our results show that the residual stresses are greatly affected by the ceramic and cemented carbide milling; both regarding depth as well as distribution across the milled slot. It has been shown that it is important to consider that the stresses across a milled slot are the highest in the center of the slot and gradually decrease toward the edges. Different inserts, ceramic and cemented carbide, and tool wear, alter how the stresses are distributed across the slot and the affected depth. © 2020 The Authors

Keywords
Carbide cutting tools; Carbide tools; Carbides; Milling (machining); Residual stresses, Allowance determination; Alloy 718; High speed milling; Material removal rate; Surface integrity, Cutting tools
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14992 (URN)10.1016/j.mtcomm.2020.100958 (DOI)000571070900004 ()2-s2.0-85079036532 (Scopus ID)
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-11-15Bibliographically approved
Tamil Alagan, N., Höier, P., Beno, T., Klement, U. & Wretland, A. (2020). Coolant boiling and cavitation wear: a new tool wear mechanism on WC tools in machining Alloy 718 with high-pressure coolant. Wear, 452-453, Article ID 203284.
Open this publication in new window or tab >>Coolant boiling and cavitation wear: a new tool wear mechanism on WC tools in machining Alloy 718 with high-pressure coolant
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2020 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 452-453, article id 203284Article in journal (Refereed) Published
Abstract [en]

In recent years, research interest in liquid coolant media applied to the tool–workpiece interface (the tertiary shear zone) has grown considerably. In particular, attention has increased for work where the media has been applied under high-pressure. This is most likely triggered by the positive results reported on similar applications, but with coolant media directed towards the rake face of the cutting tool (the secondary shear zone). The most typical applications have not surprisingly been related to the machining of Heat Resistant Super Alloys (HRSA) or other “difficult to machine” alloys where the main intention has been to extend tool life and improve surface finish through reduced shear zone temperatures. Concurrently, these achievements have revealed a knowledge gap and unlocked a new research area in understanding the effects and influences of coolant media applied on super-heated surfaces under high-pressure conditions. The aim of this study is to investigate the “coolant boiling and cavitation” phenomena that emerges during the application of coolant under high-pressure to the flank face of an uncoated WC tool while turning Alloy 718. The experimental campaign was conducted in three aspects: varying flank (coolant media) pressure; varying spiral cutting length (SCL); and varying cutting speed. The results revealed that the location and size of the coolant-boiling region correlated with flank wear, coolant pressure and vapour pressure of the coolant at the investigated pressure levels. Further, the results showed that coolant applied with a lower pressure than the vapour pressure of the coolant itself caused the “Leidenfrost” effect. This then acts as a coolant media barrier and effectively reduces the heat transport from the cutting zone. Further, erosion pits were observed on small areas of the cutting tool, resembling the typical signs of cavitation (usually found in much different applications such as pumps and propellers). The discovered wear mechanism denoted as “Cavitation Wear” was used as base for the discussion aimed to deepen the understanding of the conditions close to the sliding interface between the tool and the workpiece. Even though “Cavitation Wear” has been widely reported in hydraulic systems like pumps and water turbines, it is a new phenomenon to be seen on cutting tools while using high-pressure flank cooling. © 2020 The Authors

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Alloy 718, Coolant boiling, Cavitation wear, High-pressure coolant, Tool wear mechanism, Tungsten carbide
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-15156 (URN)10.1016/j.wear.2020.203284 (DOI)000539275700002 ()2-s2.0-85083650341 (Scopus ID)
Funder
Knowledge Foundation, 20140130Region Västra Götaland
Available from: 2020-05-04 Created: 2020-05-04 Last updated: 2020-09-10Bibliographically approved
Devotta, A. M., Sivaprasad, P. V., Beno, T. & Eynian, M. (2020). Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling. Metals, 10(4), Article ID 519.
Open this publication in new window or tab >>Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling
2020 (English)In: Metals, ISSN 2075-4701, Vol. 10, no 4, article id 519Article in journal (Refereed) Published
Abstract [en]

Machining process modeling has been an active endeavor for more than a century and it has been reported to be able to predict industrially relevant process outcomes. Recent advances in the fundamental understanding of material behavior and material modeling aids in improving the sustainability of industrial machining process. In this work, the flow stress behavior of C45E steel is modeled by modifying the well-known Johnson-Cook model that incorporates the dynamic strain aging (DSA) influence. The modification is based on the Voyiadjis-Abed-Rusinek (VAR) material model approach. The modified JC model provides the possibility for the first time to include DSA influence in chip formation simulations. The transition from continuous to segmented chip for varying rake angle and feed at constant cutting velocity is predicted while using the ductile damage modeling approach with two different fracture initiation strain models (Autenrieth fracture initiation strain model and Karp fracture initiation strain model). The result shows that chip segmentation intensity and frequency is sensitive to fracture initiation strain models. The Autenrieth fracture initiation strain model can predict the transition from continuous to segmented chip qualitatively. The study shows the transition from continuous chip to segmented chip for varying feed rates and rake angles for the first time. The study highlights the need for material testing at strain, strain rate, and temperature prevalent in the machining process for the development of flow stress and fracture models.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
chip segmentation; damage modeling; dynamic strain aging
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-15788 (URN)10.3390/met10040519 (DOI)000531826500098 ()2-s2.0-85083847260 (Scopus ID)
Funder
Knowledge Foundation, 20110263, 20140130
Available from: 2020-09-14 Created: 2020-09-14 Last updated: 2021-02-11
Holmberg, J., Wretland, A., Berglund, J. & Beno, T. (2020). Selection of milling strategy based on surface integrity investigations of highly deformed Alloy 718 after ceramic and cemented carbide milling. Journal of Manufacturing Processes, 58, 193-207
Open this publication in new window or tab >>Selection of milling strategy based on surface integrity investigations of highly deformed Alloy 718 after ceramic and cemented carbide milling
2020 (English)In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 58, p. 193-207Article in journal (Refereed) Published
Abstract [en]

High speed milling with ceramic indexable inserts is a current practice for manufacturing of gas turbine components in superalloys since it allows for high material removal rates. Ceramic milling is used for rough milling, which is followed by cemented carbide semi- and finish milling. The tool motion play an important role on the resulting surface integrity. The machining strategy of up or down milling will induce different degree of residual stresses and deformations. Increased knowledge of selecting the machining strategy with lowest impact will promote improved productivity by using ceramic milling to a greater extent based on the affected depth. The main objective in this work has been to correlate the residual stresses and deformations to promote a greater utilization of ceramic milling while still producing surfaces with acceptable properties. Prior investigations have shown that ceramic milling induce very high tensile stresses in the surface, exceeding the material’s nominal yield strength. A second objective has been to explain these stress levels by thorough investigations of the deformation after milling. In this study, milling tests with new and worn ceramic and cemented carbide inserts have been performed in Alloy 718. The topography, residual stresses, deformation and hardness have been investigated for up, centre and down milling. Residual stress measurements were performed using X-ray diffraction, followed by evaluation of hardness and deformation, using hardness testing, light optical microscopy as well as electron back scattering diffraction (EBSD). These results have been used to determine an appropriate milling strategy based on lowest possible impact in respect to residual stresses and deformation. The results show a high degree of deformation after milling that differs for the up, centre and down milling. Based on these results, it is shown that up milling is preferable for new inserts but as the inserts wear out, down milling becomes more suitable since a lower degree of deformation and residual stress impact was observed. EBSD and hardness testing showed that the milling, especially ceramic milling, caused severe deformation of the surfaces resulting in grain refinement to a nano-crystalline level. This is most likely the explanation for the prevalence of the high tensile stresses without distorting or causing failure. © 2020 The Authors

Keywords
Backscattering; Carbide tools; Carbides; Ceramics industry; Deformation; Grain refinement; Hardness; Hardness testing; Nanocrystalline materials; Petroleum reservoir evaluation; Residual stresses; Tensile stress; Topography; Well testing, Degree of deformations; Electron backscattering diffraction; Light optical microscopies; Machining strategy; Material removal rate; Milling strategies; Nominal yield strength; Severe Deformation, Milling (machining)
National Category
Other Materials Engineering Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-15771 (URN)10.1016/j.jmapro.2020.08.010 (DOI)000583414900017 ()2-s2.0-85089503058 (Scopus ID)
Funder
Vinnova, 2015-06047
Available from: 2020-09-04 Created: 2020-09-04 Last updated: 2020-12-17Bibliographically approved
Devotta, A. M., Sivaprasad, P. V., Beno, T., Eynian, M., Hurtig, K., Magnevall, M. & Lundblad, M. (2019). A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime. Metals, 9(5), Article ID 528.
Open this publication in new window or tab >>A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime
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2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 5, article id 528Article in journal (Refereed) Published
Abstract [en]

In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s-1, 5 s-1, and 60 s-1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI AG, 2019
Keywords
flow stress; modified Johnson-Cook model; dynamic strain aging
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13989 (URN)10.3390/met9050528 (DOI)000478818700046 ()2-s2.0-85066741813 (Scopus ID)
Funder
Swedish Research Council, 20110263, 20140130
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2021-06-09Bibliographically approved
Agic, A., Eynian, M., Ståhl, J. E. & Beno, T. (2019). Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries. International Journal on Interactive Design and Manufacturing, 13(2), 557-565
Open this publication in new window or tab >>Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries
2019 (English)In: International Journal on Interactive Design and Manufacturing, ISSN 1955-2513, E-ISSN 1955-2505, Vol. 13, no 2, p. 557-565Article in journal (Refereed) Published
Abstract [en]

Understanding the influence of the cutting edge geometry on the development of cutting forces during the milling process is of high importance in order to predict the mechanical loads on the cutting edge as well as the dynamic behavior on the milling tool. The work conducted in this study involves the force development over the entire engagement of a flute in milling, from peak force during the entry phase until the exit phase. The results show a significant difference in the behavior of the cutting process for a highly positive versus a highly negative cutting edge geometry. The negative edge geometry gives rise to larger force magnitudes and very similar developments of the tangential and radial cutting force. The positive cutting edge geometry produces considerably different developments of the tangential and radial cutting force. In case of positive cutting edge geometry, the radial cutting force increases while the uncut chip thickness decreases directly after the entry phase; reaching the peak value after a certain delay. The radial force fluctuation is significantly higher for the positive cutting edge geometry. The understanding of such behavior is important for modelling of the milling process, the design of the cutting edge and the interactive design of digital applications for the selection of the cutting parameters.

Keywords
Milling, Cutting force, Cutting edge geometry, Frequency spectrum, RMS
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13302 (URN)10.1007/s12008-018-0513-5 (DOI)000468115700013 ()2-s2.0-85058211299 (Scopus ID)
Funder
Knowledge Foundation
Note

Funders: Seco Tools

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2020-02-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0976-9820

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