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Jonsén, P., Svanberg, A., Ramirez, G., Casellas, D., Hernández, R., Marth, S., . . . Oldenburg, M. (2019). A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 645-652). , 7
Open this publication in new window or tab >>A Novel Method for Modelling of Cold Cutting of Microstructurally Tailored Hot Formed Components
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, Vol. 7, p. 645-652Conference paper, Published paper (Refereed)
Abstract [en]

In the last decade, hot metal forming of advanced high strength steel (AHSS) have improved passenger safety and open possibilities for lightweight design. Hot metal forming can be applied to locally tailor the microstructure of components and gradual vary mechanical properties to improve crash resistance behaviour and optimized weight for e.g. safety related parts. Sometimes post punching or trimming must be done on hardened parts. Such conditions induce damage and fractures in the trimmed edge. Another issue is that high pressures are required in cutting operations due to the high yield stress of press hardened parts, which accelerate wear and produce premature fracture in tools. Optimizing cutting operations to minimize damage and wear are essentials and numerical simulations of cutting operations can be of good assistance. One of the main challenges in the numerical modelling consists of numerically be able to treat the extremely large deformation occurring in the cutting zone. A second challenge is to find suitable failure models. In this work, the punching process of soft and hard microstructures obtained by press hardening is experimentally studied, but also modelled with a combination of smoothed particle Galerkin (SPG) method and finite element method (FEM). Laboratory punching tests with different clearance values were carried out using sheets of different fracture strengths. All experimental cases are numerically modelled. Validation is conducted by comparing numerical results with experimental measurements of punch force and displacement. In addition, morphology of the final cutting edges from both real and virtual are compared. Numerical results show good agreement against experimental measurements. Furthermore, the combined method gives robust-ness and stability as it can handle large deformations efficiently.

National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75748 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Pérez Caro, L., Schill, M., Haller, K., Odenberger, E.-L. & Oldenburg, M. (2019). Damage and fracture during sheet-metal forming of alloy 718. International Journal of Material Forming
Open this publication in new window or tab >>Damage and fracture during sheet-metal forming of alloy 718
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2019 (English)In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214Article in journal (Refereed) Epub ahead of print
Abstract [en]

Forming nickel-based superalloy aero-engine components is a challenging process, largely because of the risk of high degree of springback and issues with formability. In the forming tests conducted on alloy 718 at room temperature, open fractures are observed in the drawbead regions, which are not predicted while evaluating the formability using the traditional forming-limit diagram(FLD). This highlights the importance of an accurate prediction of failure during forming as, in some cases, may severely influence the springback and thereby the accuracy of the predicted shape distortions, leading the final shape of the formed component out of tolerance. In this study, the generalised incremental stress-state dependent damage model (GISSMO) is coupled with the isotropic von Mises and the anisotropic Barlat Yld2000-2D yield criteria to predict the material failure in the forming simulations conducted on alloy 718 using LS-DYNA. Their effect on the predicted effective plastic strains and shape deviations is discussed. The failure and instability strains needed to calibrate the GISSMO are directly obtained from digital image correlation (DIC) measurements in four different specimen geometries i.e. tensile, plane strain, shear, and biaxial. The damage distribution over the drawbeads is measured using a non-linear acoustic technique for validation purposes. The numerical simulations accurately predict failure at the same regions as those observed in the experimental forming tests. The expected distribution of the damage over the drawbeads is in accordance with the experimental measurements. The results highlight the potential of considering DIC to calibrate the GISSMO in combination with an anisotropic material model for forming simulations in alloy 718.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
alloy 718, damage, fracture, GISSMO, non-linear acoustic technique, optimisation
National Category
Metallurgy and Metallic Materials Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62903 (URN)10.1007/s12289-018-01461-4 (DOI)
Projects
Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)
Funder
Vinnova, 2013-01173
Available from: 2017-04-05 Created: 2017-04-05 Last updated: 2019-10-07
Marth, S., Golling, S., Östlund, R., Barrero Pijoan, A., Häggblad, H.-Å. & Oldenburg, M. (2019). Failure Modelling and Experimental Evaluation of a Press-Hardened Laboratory Scale Component with Multi-Phase Microstructure. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 39-50). , 7, Article ID B1.
Open this publication in new window or tab >>Failure Modelling and Experimental Evaluation of a Press-Hardened Laboratory Scale Component with Multi-Phase Microstructure
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, Vol. 7, p. 39-50, article id B1Conference paper, Published paper (Refereed)
Abstract [en]

Hot stamping of boron alloyed steel has become a standard in the automotive industry for safety relevant body in white components. This process allows the design of complex geometries with superior mechanical properties. Special tool design enables to manufacture components with special properties based on varying microstructures in designated areas. This is a challenge for finite element (FE) simulations of deformation and failure for multi-phase microstructure components.

In the present work, a laboratory scale test component with multi-phase microstructure is studied from blank to fractured component. Using different tool temperatures and adding an air-cooling step before transfer to the press hardening tool, the microstructure of the component is varied. By this, components with four different multi-phase microstructures are produced. These components are tested under tensile deformation until fracture, where force, elongation and the strain field on the components surface are measured.

The laboratory scale test component is evaluated using FE-modelling. The complete production process is modelled starting with the pre-cut austenitized blank, subsequent transfer, air-cooling, forming operation, and the final post-cooling. The resulting multi-phase micro structures are evaluated using manual optical microscope image analysis and compared with the simulated phase composition. Furthermore, the deformation and fracture of the manufactured component under tensional loading is studied using a mean-field homogenization scheme for the multi-phase composition combined with the OPTUS failure model. This finite element investigation is conducted taking the microstructure composition, shape and thickness deviations from the forming simulation into account.

The present work shows the feasibility of modelling methods of the complete process chain for press-hardened components with multi-phase microstructures, from blank to fractured component.

National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75739 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-09-06
Odenberger, E.-L., Pederson, R. & Oldenburg, M. (2019). Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets. The International Journal of Advanced Manufacturing Technology, 104(9-12), 3439-3455
Open this publication in new window or tab >>Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets
2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 104, no 9-12, p. 3439-3455Article in journal (Refereed) Published
Abstract [en]

In this work, a hot forming procedure is developed using computer-aided engineering (CAE) to produce thin Ti-6Al-4V sheet components in an effective way. Traditional forming methods involve time- and cost-consuming furnace heating and subsequent hot sizing steps. A material model for finite element (FE) analyses of sheet metal forming and springback at elevated temperatures in Ti-6Al-4V is calibrated and evaluated. The anisotropic yield criterion proposed by Barlat et al. 2003 is applied, and the time- and temperature-dependent stress relaxation behavior for elastic and inelastic straining are modeled using a Zener–Wert–Avrami formulation. Thermo-mechanical uniaxial tensile tests, a biaxial test, and uniaxial stress relaxation tests are performed and used as experimental reference to identify material model parameters at temperatures up to 700 °C. The hot forming tool setup is manufactured and used to produce double-curved aero engine components at 700 °C with different cycle times for validation purposes. Correlations between the predicted and measured responses such as springback and shape deviation show promising agreement, also when the forming and subsequent holding time was as low as 150 s. The short cycle time resulted in elimination of a detectable alpha case layer. Also, the tool surface coating extends the tool life in combination with a suitable lubricant. 

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Hot forming, Stress relaxation, Springback, Ti-6Al-4V, Plastic anisotropy, FE analysis
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-75356 (URN)10.1007/s00170-019-04071-9 (DOI)
Note

Validerad;2019;Nivå 2;2019-11-27 (johcin)

Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-11-27Bibliographically approved
Frómenta, D., Parareda, S., Lara, A., Casellas, D., Pujante, J., Jonsén, P., . . . Oldenburg, M. (2019). Fracture Toughness Evaluation of Thick Press Hardened 22MnB5 Sheets for High Crash Performance Applications in Trucks. In: Mats Oldenburg, Jens Hardell, Daniel Casellas (Ed.), CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019 (pp. 113-121).
Open this publication in new window or tab >>Fracture Toughness Evaluation of Thick Press Hardened 22MnB5 Sheets for High Crash Performance Applications in Trucks
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019 / [ed] Mats Oldenburg, Jens Hardell, Daniel Casellas, 2019, p. 113-121Conference paper, Published paper (Refereed)
National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-75751 (URN)
Conference
CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29
Deng, L., Pelcastre, L., Hardell, J., Prakash, B. & Oldenburg, M. (2019). Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces. Engineering Failure Analysis, 99, 85-96
Open this publication in new window or tab >>Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces
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2019 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 99, p. 85-96Article in journal (Refereed) Published
Abstract [en]

Press hardened steels are commonly used as a lightweight choice for manufacturing car components because of the high ratio of strength to weight. The use of ultra-high-strength steels for the design of lightweight vehicles contributes to the reduction of emissions of carbon dioxide while maintaining passenger safety. Stamping tools used in press hardening processes suffer harsh contact conditionsin terms of dramatic temperature changes, cyclic loadings, and complex interactions between coatings and oxidation. In mass production, tool wear is an inevitable problem that increases maintenance costs. Severe adhesive wear, also called galling, substantially occurs in the stamping tool used against Al—Si-coated workpieces. The galling that takes place during press hardening not only degrades the production quality but also shortens the service life of the tool. In order to properly arrange tool maintenance and minimize galling through adjusting process parameters, engineers need to know when and where galling occurs, based on modelling of the galling in press hardening simulations. In order to implement a galling simulation for press hardening, a modified Archard wear model is employed in the present study, which is a contact-mechanics-based model. The specific wear rate in the model is calibrated by the quantitative galling measurements of a high-temperature tribometer test. The tribological test is designed to mimic the press hardening conditions, where the correlations between galling and process parameters such as temperature, pressure, and sliding distance are outlined. The galling simulation is implemented in a full-scale press hardening experiment, and the predicted galling is validated in terms of severe galling positions and galling profiles. The galling profile evolution is correlated to variations in the contact conditions. Uncertainties in the numerical model, such as the choice of penalty scaling factor and friction coefficient, are analysed with a parameter study and discussed. This study demonstrates finite element (FE) simulations involving galling prediction in press hardening so as to improve product development and production efficiency.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Contact conditions, High-temperature tribometer, FE simulation, Galling prediction
National Category
Applied Mechanics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Solid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73044 (URN)10.1016/j.engfailanal.2019.01.059 (DOI)000464957800008 ()2-s2.0-85061604416 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-27 (johcin)

Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-05-02Bibliographically approved
Deng, L., Pelcastre, L., Hardell, J., Prakash, B. & Oldenburg, M. (2018). Experimental Evaluation of Galling Under Press Hardening Conditions. Tribology letters, 66(3), Article ID 93.
Open this publication in new window or tab >>Experimental Evaluation of Galling Under Press Hardening Conditions
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2018 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 3, article id 93Article in journal (Refereed) Published
Abstract [en]

Severe adhesion, also referred to as galling, is a critical problem in press hardening, especially in stamping tools used for hot forming of Al–Si-coated ultra-high strength steel. Galling is known to develop rapidly on the tool surface and it negatively affects the quality of the formed products. Earlier research on this topic has focused on the galling initiation. However, studies on the galling development during extended sliding and the corresponding quantitative measurement still lack depth. In the present study, a tribological test is established to study the galling development under press hardening conditions. The tribological test set-up aims to simulate extended sliding between the Al–Si-coated boron steels and the tool die material. The contact conditions in the interface are studied by a numerical model of the tribological test. The friction coefficients and material transfer are discussed taking into account the variation of the different test conditions. Using the results from the tribological tests, the galling simulation is performed in the numerical model. A geometry-updated sample based on the galling (transferred material build-up) height is simulated and the consequent pressure fluctuation is obtained in the numerical model. This contributes to the explanation of the severe transferred material accumulation during the test.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Machine Elements; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-69943 (URN)10.1007/s11249-018-1023-0 (DOI)000436540000001 ()2-s2.0-85049356784 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-27 (andbra)

Available from: 2018-06-27 Created: 2018-06-27 Last updated: 2018-07-23Bibliographically approved
Marth, S., Golling, S., Östlund, R. & Oldenburg, M. (2018). From Blank to Fractured Component: Numerical and Experimental Results of a Laboratory Scale Component. In: : . Paper presented at International Deep Drawing Research Group 37th Annual Conference 3–7 June 2018, University of Waterloo, Waterloo, Ontario, Canada. Institute of Physics (IOP), 418, Article ID 012008.
Open this publication in new window or tab >>From Blank to Fractured Component: Numerical and Experimental Results of a Laboratory Scale Component
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Hot stamping of boron alloyed steel has become a standard in the automotive industry for safety relevant chassis components. Hot stamping of ultra-high strength steel allows the design of complex geometries with superior mechanical properties. In the present work, a laboratory scale test component is followed up from blank to fractured component. The production process starts with a pre-cut blank, which then is austenitized, transferred to the press hardening tool, formed and quenched and ends with post-cooling to room temperature. These components are tested under tensile deformation until fracture, where force, elongation and the strain field on the components surface are measured. The strain field measurements are performed by using digital image correlation (DIC). The laboratory scale test component is evaluated using finite element modelling. The production process is modelled starting with a pre-cut austenitized blank, subsequent transfer and forming operation, and ends with post-cooling. Furthermore, the deformation and fracture under tension/bending is studied using the OPTUS damage model. The as-produced component is measured using a three dimensional scanning system. Shape deviation and thickness change are compared to in the forming simulation predicted geometry after post-cooling. A finite element investigation on the deformation and fracture under tensional/bending loading is conducted applying shape and thickness deviations in the model. The majority of industrial components undergo paint curing before they are included in an assembly. Paint baking is a heat treatment at relatively low temperatures and causes relaxation in a martensitic microstructure. The effect of paint baking on the mechanical response of the laboratory scale test component is investigated. In the present work the reliability of modelling tools from blank to fractured component is shown. The possibility is shown to predict the failure of the component, with the specific phase composition after the hot stamping process obtained from simulations. Furthermore, the influence of the paint baking process on the mechanical properties is presented.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2018
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71045 (URN)10.1088/1757-899X/418/1/012008 (DOI)2-s2.0-85054247283 (Scopus ID)
Conference
International Deep Drawing Research Group 37th Annual Conference 3–7 June 2018, University of Waterloo, Waterloo, Ontario, Canada
Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-12-21Bibliographically approved
Odenberger, E.-L., Pérez Caro, L., Åhlin, H. & Oldenburg, M. (2018). Thermo-mechanical Material Characterization and Stretch-bend Forming of AA6016. Paper presented at International Deep Drawing Research Group 37th Annual Conference 3–7 June 2018, University of Waterloo, Waterloo, Ontario, Canada. IOP Conference Series: Materials Science and Engineering, 418, Article ID 012022.
Open this publication in new window or tab >>Thermo-mechanical Material Characterization and Stretch-bend Forming of AA6016
2018 (English)In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 418, article id 012022Article in journal (Refereed) Published
Abstract [en]

Lightweight design has become increasingly in focus for the manufacturing industry. Global environmental challenges, goals and legislations imply that lighter and sustainable products are imperative to remain competitive. One example is stamped products made of aluminum alloys which are of interest to the automotive industry, where lightweight designs are essential. In order to increase formability and to produce more complex geometries in stamped aluminum components there is a need to develop hot forming techniques. The Finite Element Method (FEM) has enabled important advances in the study and design of competitive manufacturing procedures for metal parts. Predicting the final geometry of a component is a complex task, especially if the forming procedure occurs at elevated temperatures. This work presents selected results from thermo-mechanical material testing procedures, FE-analyses and forming validation tests in AA6016 material. The material tests are used to determine the thermo-mechanical anisotropic properties, strain rate sensitivity and formability (Forming Limit Curves, FLC) at temperatures up to 490°C. Stretch-bending tests are performed to compare predicted results with experimental observations such as punch force, strain levels, thinning, forming temperatures, springback and failure. It was found that the heat-treatment and forming at elevated temperatures substantially increased formability and that measured responses could in general be predicted if care was taken to model the initial blank temperatures, heat transfer and thermo-mechanical material properties. The room temperature case confirms the importance of considering anisotropy.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2018
National Category
Applied Mechanics Other Civil Engineering
Research subject
Solid Mechanics; Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-71364 (URN)10.1088/1757-899X/418/1/012022 (DOI)2-s2.0-85054260019 (Scopus ID)
Conference
International Deep Drawing Research Group 37th Annual Conference 3–7 June 2018, University of Waterloo, Waterloo, Ontario, Canada
Note

Konferensartikel i tidskrift;2018-10-30 (svasva)

Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2019-01-11Bibliographically approved
Mozgovoy, S., Hardell, J., Deng, L., Oldenburg, M. & Prakash, B. (2018). Tribological Behavior of Tool Steel under Press Hardening Conditions Using Simulative Tests. Journal of tribology, 140(1), Article ID 011606.
Open this publication in new window or tab >>Tribological Behavior of Tool Steel under Press Hardening Conditions Using Simulative Tests
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2018 (English)In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 140, no 1, article id 011606Article in journal (Refereed) Published
Abstract [en]

Press hardening is employed in the automotive industry to produce advanced high-strength steel components for safety and structural applications. This hot forming process depends on friction as it controls the deformation of the sheet. However, friction is also associated with wear of the forming tools. Tool wear is a critical issue when it comes to the dimensional accuracy of the produced components and it reduces the service life of the tool. It is therefore desirable to enhance the durability of the tools by studying the influence of high contact pressures, cyclic thermal loading, and repetitive mechanical loading on tool wear. This is difficult to achieve in conventional tribological testing devices. Therefore, the tribological behavior of tool-workpiece material pairs at elevated temperatures was studied in a newly developed experimental setup simulating the conditions prevalent during interaction of the hot sheet with the tool surface. Uncoated 22MnB5 steel and aluminum-silicon (Al-Si)-coated 22MnB5 steel were tested at 750 °C and 920 °C, respectively. It was found that higher loads led to lower and more stable friction coefficients independent of sliding velocity or surface material. The influence of sliding velocity on the coefficient of friction was only marginal. In the case of Al-Si-coated 22MnB5, the friction coefficient was generally higher and unstable due to transfer of Al-Si coating material to the tool. Adhesion was the main wear mechanism in the case of uncoated 22MnB5

Place, publisher, year, edition, pages
The American Society of Mechanical Engineers (ASME), 2018
National Category
Applied Mechanics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Solid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-65268 (URN)10.1115/1.4036924 (DOI)000415376300018 ()2-s2.0-85027285991 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-08-28 (andbra)

Available from: 2017-08-23 Created: 2017-08-23 Last updated: 2018-11-27Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7074-8960

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