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Gebretsadik, D., Hardell, J. & Prakash, B. (2019). Embeddability behaviour of some Pb-free engine bearing materials in the presence of abrasive particles in engine oil. Tribology - Materials, Surfaces & Interfaces, 13(1), 39-49
Open this publication in new window or tab >>Embeddability behaviour of some Pb-free engine bearing materials in the presence of abrasive particles in engine oil
2019 (English)In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 13, no 1, p. 39-49Article in journal (Refereed) Published
Abstract [en]

One of the tribological requirements on engine bearing material is its ability to safely embed contaminant particles onto its surface and minimise damage to both the bearing and crankshaft surfaces. In this work, a journal bearing test rig that operates under constant load has been employed to investigate the embeddability behaviour of selected multi-layered Pb-free engine bearing materials at three different rotational speeds using engine oil contaminated with SiC particles. Experimental results have shown that third-body abrasive wear is influenced by the lubricant film thickness. There was also difference in embeddability of the different materials. Bismuth-based overlay and MoS2 containing polyamide-imide-based overlay-coated materials show higher wear compared to tin-based overlay and a polyamide-imide-based composite overlay-coated material. Steel counter surfaces sliding against bismuth-based overlay and MoS2 containing polyamide-imide-based overlay exhibited higher wear than those sliding against tin-based overlay and polyamide-imide-based composite overlay. 

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Embeddability, third-body abrasive wear, hydrodynamic lubrication, engine bearings, Pb-free
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-72774 (URN)10.1080/17515831.2019.1574452 (DOI)000471166200005 ()
Note

Validerad;2019;Nivå 2;2019-04-12 (oliekm)

Available from: 2019-02-04 Created: 2019-02-04 Last updated: 2019-07-01Bibliographically approved
Mozgovoy, S., Hardell, J. & Prakash, B. (2019). High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions. Advances in Tribology, 2019, Article ID 4981246.
Open this publication in new window or tab >>High Temperature Friction and Wear Performance of PVD Coatings under Press Hardening Contact Conditions
2019 (English)In: Advances in Tribology, ISSN 1687-5915, E-ISSN 1687-5923, Vol. 2019, article id 4981246Article in journal (Refereed) Published
Abstract [en]

Press hardening is widely employed to produce automotive structural and safety components from advanced high-strength steels. This process depends on friction between the forming tools and the work piece. Wear of the forming tools affects the dimensional accuracy of produced components and reduces their service life. It is therefore desirable to reduce wear of forming tools for press hardening applications. One way to achieve this is by applying hard physical vapour deposited (PVD) coatings on the tool. In this work, the tribological behaviour of PVD coated tool-work piece material pairs has been studied at elevated temperatures in an experimental set-up simulating the tribological conditions in press hardening. Four different PVD coatings deposited on tool steel and uncoated tools as reference were studied during sliding against uncoated and Al-Si coated 22MnB5 steel. Results show that uncoated tools exhibited the lowest coefficient of friction when sliding against uncoated 22MnB5 steel. A CrWN coating initially showed low coefficient of friction but it increased with increasing sliding distance. A TiAlN coating and one of two AlCrN coatings showed similar frictional behaviour when sliding against uncoated 22MnB5 steel. During sliding against uncoated 22MnB5 steel, adhesive wear has been found to be the dominant wear mechanism. Adhesive wear was considerably reduced in the case of hard PVD coated tools in comparison to that of uncoated tools. During sliding against Al-Si coated 22MnB5 steel, no clear advantage in terms of friction behaviour of uncoated or PVD coated tools was observed. However, the transfer of Al-Si coating material from the work piece to the tools was significantly reduced for PVD coated tools. Frictional instabilities in all cases involving Al-Si coated work piece material further confirmed the occurrence of adhesive material transfer.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73812 (URN)10.1155/2019/4981246 (DOI)000466291800001 ()2-s2.0-85065224213 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-05-02 (johcin)

Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-06-25Bibliographically approved
Mozgovoy, S., Alik, L., Hardell, J. & Prakash, B. (2019). Material transfer during high temperature sliding of Al-Si coated 22MnB5 steel against PVD coatings with and without aluminium. In: Wear of Materials: . Paper presented at 22nd International Conference on Wear of Materials, April 14-18 2019, Miami, USA (pp. 401-411). Elsevier, 426-427
Open this publication in new window or tab >>Material transfer during high temperature sliding of Al-Si coated 22MnB5 steel against PVD coatings with and without aluminium
2019 (English)In: Wear of Materials, Elsevier, 2019, Vol. 426-427, p. 401-411Conference paper, Published paper (Refereed)
Abstract [en]

Press hardening of Al-Si coated 22MnB5 steel is the dominant technology to enable light weight design in automotive applications. Transfer of the Al-Si coating onto the tool surface occurs during hot forming. This affects process economy and quality of produced components. The reported galling mechanisms are adhesion and compaction of wear debris. Surface engineering of forming tools has been proposed to minimise the transfer of Al-Si coating. Plasma nitriding of tool steel surfaces reduces adhesion but has poor abrasive wear resistance. PVD coatings have generally been found to promote galling due to higher chemical affinity but improve abrasive wear resistance. Most studied PVD coatings are transition metal nitrides containing aluminium. The aim of this study is to investigate the role of aluminium in PVD coatings and its effect on transfer of Al-Si coating material during sliding against coated tool steel at high temperatures. This work has focussed on PVD coatings (AlCrN and CrWN) deposited on plasma nitrided tool steel. Their tribological behaviour was studied using a hot strip-drawing tribometer capable of simulating the conditions prevalent in press hardening. The results showed that PVD coatings containing aluminium induce more material transfer. The material transfer is mainly related to chemical affinity since all coatings were polished to a low surface roughness (Sa =~120 nm) to minimise transfer initiated by surface defects. The hardness of the PVD coatings does not seem to influence the material transfer since the softer coating (CrWN, HV0.05 = ~1850) showed less transfer compared to AlCrN (HV0.05 = ~2100). The CrWN coating showed longer running-in compared to AlCrN due to reduced initial material transfer. Formation of thicker transfer layers governs the steady state friction mechanisms. Material transfer of Fe-Al intermetallic compounds occurs at the initial stages of sliding through direct adhesion to the PVD coating. The layers grow to > 5 µm thickness within a few decimetres of sliding.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Friction, Wear, High temperature, PVD coating, Aluminium
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73686 (URN)10.1016/j.wear.2018.12.042 (DOI)000464583700043 ()
Conference
22nd International Conference on Wear of Materials, April 14-18 2019, Miami, USA
Available from: 2019-04-17 Created: 2019-04-17 Last updated: 2019-04-30Bibliographically approved
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
Moghaddam, P. V., Hardell, J., Vuorinen, E. & Prakash, B. (2019). The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels. Wear, 428-429, 193-204
Open this publication in new window or tab >>The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels
2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 428-429, p. 193-204Article in journal (Refereed) Published
Abstract [en]

The dry rolling/sliding wear of nanostructured bainite has been investigated and compared with that of a conventional quenched and tempered bearing steel. In order to elucidate the role of retained austenite on the wear performance, high silicon hypereutectoid bearing steel with an identical alloy composition was heat treated to obtain different microstructures with similar hardness and different amounts of retained austenite. The results indicate that the nanostructured bainite can meet the minimum hardness requirements for bearing applications. Moreover, the nanostructured bainite outperformed the tempered martensitic steel in terms of wear resistance. The work hardening capacity and thus wear resistance increases due to the transformation of retained austenite into martensite. The results of XRD analyses show that the higher stability of retained austenite and strength of bainitic ferrite leads to better wear performance. It is demonstrated that the stability of retained austenite outweigh the influence of retained austenite content on wear resistance. Adhesion and oxidation were identified as the main wear mechanisms. In addition to microstructure, surface oxidation also plays a prominent role in determining the wear resistance. 

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Bearings, Carbide-free bainite, Nanostructured materials, Retained austenite, Rolling-sliding, TRIP effect
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73366 (URN)10.1016/j.wear.2019.03.012 (DOI)000471596300019 ()2-s2.0-85063237323 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-04-01 (svasva)

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-07-10Bibliographically approved
Decrozant-Triquenaux, J., Pelcastre, L., Courbon, C., Prakash, B. & Hardell, J. (2019). Tribological Behaviour of PVD Coated Tool Steels in Hot Forming of Aluminium Alloys. In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel: . Paper presented at CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, Luleå, Sweden, June 2nd to 5th 2019.
Open this publication in new window or tab >>Tribological Behaviour of PVD Coated Tool Steels in Hot Forming of Aluminium Alloys
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2019 (English)In: CHS² 2019 - 7th International Conference on Hot Sheet Metal Forming of High Performance Steel, 2019Conference paper, Published paper (Refereed)
Abstract [en]

Aluminium alloys are commonly used as light-weight materials in the automotive industry. Thisnon-ferrous family of metal alloys offers high versatility of properties and designs. In order to reduceweight and improve safety, grades with high strength-to-weight ratio, such as the 6XXX and 7XXXalloy series, are increasingly implemented in vehicles. These alloys, however, exhibit low formabilityand experience considerable springback when formed at low temperatures, and thus have to beformed at elevated temperatures. Severe adhesion and galling are known to be critical tribologicalchallenges in hot forming of aluminium. During the forming operation, adhesion and transfer ofaluminium onto the die surface take place. This phenomenon has a detrimental effect on the surfaceproperties, geometrical tolerances of the formed parts and maintenance of the dies. The influence ofsurface engineering as well as lubricant composition on adhesion and galling has not been sufficientlyinvestigated. Diamond-like-Carbon and Chromium Nitride PVD coatings applied on the toolsteel have shown promising results for reducing aluminium transfer at high-temperatures, especiallyin the presence of a lubricant. However, the interaction between lubricants and PVD coatings duringhot forming of aluminium alloys is not yet fully understood. The present study thus aims at characterisingthe high temperature tribological behaviour of selected PVD coatings and a lubricant duringsliding against an aluminium alloy. The objectives are to select promising lubricant-coating combinationsfor the given application and to study their tribological response in a high-temperature reciprocatingfriction and wear tester. The tests were carried out at 300°C, under dry and lubricatedconditions, in order to study the friction and wear performance. Uncoated tool steel reference testswere performed under dry and lubricated conditions and lubricated tests using DLC, CrN, CrTiNand CrAlN coated tool steel were performed and compared to the reference results. The initial andworn surfaces were analysed with white light 3D optical interferometry, scanning electron microscopy(SEM) and energy dispersive spectroscopy (EDS) with a view to understand the wear mechanisms.

Keywords
high temperature tribology, aluminium, lubrication, PVD coatings, material transfer, adhesion
National Category
Mechanical Engineering
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73799 (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: 2019-04-30 Created: 2019-04-30 Last updated: 2019-08-13
Decrozant-Triquenaux, J., Pelcastre, L., Prakash, B. & Hardell, J. (2018). Effect of Surface Engineered Tool Steels on Frition and Wear During Sliding Against Aluminium at High Temperatures. In: Uppsala University (Ed.), The 18th Nordic Symposium on Tribology – NORDTRIB 2018, Uppsala, Sweden, 18-21 June 2018: . Paper presented at The 18th Nordic Symposium on Tribology – NORDTRIB 2018.
Open this publication in new window or tab >>Effect of Surface Engineered Tool Steels on Frition and Wear During Sliding Against Aluminium at High Temperatures
2018 (English)In: The 18th Nordic Symposium on Tribology – NORDTRIB 2018, Uppsala, Sweden, 18-21 June 2018 / [ed] Uppsala University, 2018Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Usage of high-strength aluminium alloys is increasing for automotive applications due to high strength-to-weight ratios. Limited formability at room temperature requires hot forming for production of complex geometries. The occurrence of severe adhesion and material transfer negatively affects process economy and there is a need for effective solutions to overcome these issues. This work is focussed on the high-temperature tribological behaviour of Al6016 alloy and uncoated/PVD coated tool steels. Studies were conducted under dry and lubricated conditions using a high-temperature reciprocating tribometer. High friction in dry sliding for uncoated and coated tool steels was observed. Hexagonal boron nitride lubricant was not effective in reducing friction. DLC coating with a polymer lubricant resulted in the lowest friction and minimised material transfer.

Keywords
friction, wear, high temperature, aluminium, lubrication
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73798 (URN)
Conference
The 18th Nordic Symposium on Tribology – NORDTRIB 2018
Available from: 2019-04-30 Created: 2019-04-30 Last updated: 2019-08-13
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
Hernandez, S., Hardell, J. & Prakash, B. (2018). High-Temperature Friction and Wear of Boron Steel and Tool Steel in Open and Closed Tribosystems. Tribology Transactions, 61(3), 448-458
Open this publication in new window or tab >>High-Temperature Friction and Wear of Boron Steel and Tool Steel in Open and Closed Tribosystems
2018 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, no 3, p. 448-458Article in journal (Refereed) Published
Abstract [en]

More and more components in automotive, material processing and mining industries are operating under harsh conditions involving high temperatures and high contact pressures. Tribotesting for such applications is done using both open (one surface meeting a fresh counter-surface) and closed (one surface follows the same track on the counter-surface) test configurations. In order to enable development of new materials and processes intended for such conditions, there is a need for better understanding pertaining to tribological phenomena occurring under these different test configurations.

In this work, friction and wear characteristics of quenched and tempered tool steel sliding against boron steel (22MnB5) have been studied. The experiments were conducted using a specially designed hot strip tribometer (HST) under dry conditions at R.T. and 400°C in open as well as closed configurations. Scanning electron microscopy/energy dispersive spectroscopy and X-ray techniques were carried out to analyse the worn surfaces. Additionally, the results from the closed test configuration were compared to previous tests carried out with the same materials and parameters using a pin-on-disk (POD) test rig. The results have shown that wear was reduced at higher temperatures as well as with repeated sliding on the same contacting surfaces (i.e. closed configuration) compared to those with open configuration. A good correlation of wear mechanisms and coefficient of friction between closed configuration tests and those carried out with the POD test rig was observed especially at 400°C.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-65170 (URN)10.1080/10402004.2017.1350310 (DOI)000444573200006 ()2-s2.0-85028558287 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-08 (johcin) 

Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2018-10-08Bibliographically approved
Gebretsadik, D., Hardell, J. & Prakash, B. (2018). Seizure behaviour of Pb-free engine bearing materials under dry condition. Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, 232(2), 106-116
Open this publication in new window or tab >>Seizure behaviour of Pb-free engine bearing materials under dry condition
2018 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 2, p. 106-116Article in journal (Refereed) Published
Abstract [en]

Due to new environmental regulations, Pb-free engine bearing materials are becoming more common and there is a need for studying their tribological performance. Under severe operating conditions, failure due to seizure can occur in engine bearings. In this work, seizure behaviour of different multi-layered engine bearing materials has been studied by using a block-on-ring test setup under dry condition. These materials included Al–Sn-based lining with no overlay, bronze lining with polyamide-imide-based overlay containing MoS2 and graphite, bronze lining with two overlays of Al–Sn-based and polyamide-imide-based material, bronze-based lining with Sn-based overlay and bismuth (Bi)-containing bronze with Sn-based overlay. The tests were performed by gradually increasing the load at a specific time interval and in a stepwise manner and at a constant speed under unidirectional dry sliding conditions. The test materials, counter surfaces and the wear debris were analysed using SEM with a view to understand the seizure mechanisms. Bronze-based lining with a polyamide-imide-based overlay containing MoS2 and graphite does not exhibit seizure up to a load of 475 N. For Al–Sn-based lining without overlay, seizure occurs at a relatively lower load of 125 N. The Al–Sn-based lining with no overlay shows higher friction and the polyamide-imide-based overlay containing MoS2 and graphite shows lower friction during the seizure test. In most cases, there is material transfer onto the test ring counter surface. Material transfer onto the counter surface either due to severe adhesion or wear debris adhered and smeared on it. Al–Sn-based lining and an exposed Al–Sn-based overlay show severe adhesion that causes seizure. On the other hand, exposed Pb containing lining and Bi containing lining seize due to mechanical interlocking caused by the adhered wear debris on both surfaces.

Place, publisher, year, edition, pages
Sage Publications, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-63437 (URN)10.1177/1350650117706641 (DOI)000424781600002 ()2-s2.0-85042873912 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-02-12 (svasva)

Available from: 2017-05-18 Created: 2017-05-18 Last updated: 2018-03-16Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1162-4671

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