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  • 1.
    Aiso, Toshiharu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubota, Manabu
    Nippon Steel & Sumitomo Metal Corporation.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of Mn and Al additions to carbon steel on material transfer and coating damage mechanism in a sliding contact between steel and TiN coated HSS tool2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 101, p. 414-424Article in journal (Refereed)
    Abstract [en]

    A crossed cylinders sliding test, simulating the contact between the chip and the cutting tool, is used to evaluate material transfer, friction characteristics and coating damage of a TiN coated high speed steel against specifically designed model steels. These steels include one reference with C as the only alloy element (Base steel), and two alloyed also with 1 mass% Mn or Al. When sliding against the Base steel, an Fe–O layer forms on the coating and protects it from wear. Against the Mn alloyed steel, Fe–Mn–O forms, which has no protective effect. Against the Al alloyed steel, an almost pure Al–O layer forms. This leads to the highest friction, rapidly causing substrate softening and coating fracture.

  • 2.
    André, Benny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Comparisons between commercial low-friction coatings and emerging coating concepts in ball-on-disc tests – coefficient of friction, tribofilm formation and surface damage2008Conference paper (Refereed)
  • 3.
    Angserud, Jenny
    et al.
    Sandvik Mining.
    From, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wallin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Norgren, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On a wear test for rock drill inserts2013Conference paper (Refereed)
    Abstract [en]

    In this work wear of cemented carbide rock drill inserts is evaluated by using a rotating rock cylinder as counter surface. The influence on wear rate and degradation mechanisms from varying dry and wet conditions, cemented carbide grade, abrasive particle type and size as well as load is studied. The used abrasive media are alumina and silica.

    Test results show high repeatability and the three tested cemented carbide grades can be differentiated, even though their relative difference in sample hardness is modest. The loads used, 100–200 N, are sufficiently high to cause fracture and wear of the granite rock. The degraded microstructure of inserts tested under wet and dry conditions as well as with added silica particles is similar to field worn inserts. Hence, the same wear mechanisms occur and the test successfully mimics rock drill wear. Typical insert wear includes cracking and fragmentation of WC grains, depletion of Co binder phase and adhered material originating from the rock.

    Tests under dry conditions always cause less measured wear than tests under wet conditions.

    Addition of alumina particles, which are harder than the used cemented carbide samples, causes a significant wear rate increase but does not provide wear similar to rock drilling.

  • 4.
    Bejjani, Roland
    et al.
    Sandvik Coromant Västberga.
    Marianne, Collin
    Sandvik Coromant Västberga.
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Stina, Odelros
    Sandvik Coromant Västberga.
    Multi-scale study of initial tool wear on textured alumina coating, and the effect of inclusions in low-alloyed steel2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 100, p. 204-212Article in journal (Refereed)
    Abstract [en]

    When turning low-alloyed steel with hard inclusions, scores and grooves have been observed in the wear of the alumina coating in CVD coated cutting tools. This study focuses on detailed understanding of flank wear in the textured alumina coating and the relation to the workpiece's inclusions. For chip formation studies, a quick stop device has been used. A topography analysis for the worn coating was performed in the micro scale. Studies at lower scales were performed using TEM. This allowed the study of wear on the coating crystalline structure and the embedment of workpiece material on its surface. Based on the results, the mechanism behind the initial wear was analyzed and an abrasion wear model is proposed.

  • 5.
    Braceras, Inigo
    et al.
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Ibanez, Inigo
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Taher, Mamoun
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    del Barrio, Andres
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Saenz De Urturi, Saioa
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    ABB AB, Corp Res, Insulat & Mat Technol, SE-72178 Vasteras, Sweden.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    On the electro-tribological properties and degradation resistance of silver-aluminum coatings2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 414, p. 202-211Article in journal (Refereed)
    Abstract [en]

    Contact materials in sliding electrical applications must possess low electrical contact resistance, low friction and wear coefficients, and high degradation resistance to the surrounding media. Silver coatings are commonly used in such applications despite their shortcomings. This work has focused on the study of alternative silver-aluminum coatings deposited by PVD. The main findings include the strong dependence of the tribological performance on the concentration of Al and hence the phases present in the coatings. Besides, the wear mechanism was found to be affected by the working media, either on air or insulating oil. Results have shown that for full HCP phase coatings (Ag67Al33), wear rates are lowest, with no adhesive wear and good surface sulphidation resistance, though with some proclivity to oxidation, coupled with a moderate increase in the electrical contact resistance.

  • 6.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Heldin, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale2019In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed)
    Abstract [en]

    With industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.

  • 7.
    Eskildsen, Svend
    et al.
    MAN Diesel & Turbo.
    Fogh, Jesper
    MAN Diesel & Turbo.
    Andersson, Henrik
    Olander, Petra
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On the sulphuric acid corrosion in large 2-stroke marine diesel engines2014In: Tribocorrosion 2014,  9-11 April 2014, University of Strathclyde, Glasgow, 2014Conference paper (Refereed)
  • 8.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Combustion Valve Wear: A Tribological Study of Combustion Valve Sealing Interfaces2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The exhaust valve system of combustion engines experiences a very complex contact situation of frequent impact involving micro sliding, high and varying temperatures, complex exhaust gas chemistry and possible particulates, etc. In addition, the tribological situation in the exhaust valve system is expected to become even worse due to strict future emission regulations, which will require enhanced combustion and cleaner fuels. This will substantially reduce the formation of combustion products that might ease the contact conditions by forming tribofilms on the contacting surfaces. The lack of protective films is expected to result in increased wear of the contact surfaces.

    The aim of the work presented in this thesis has been to increase the tribological understanding of the valves. The wear that takes place in the valve sealing interface and how the change in operating conditions affects it have been studied. Such understanding will facilitate the development of future valve designs.

    A test rig has been developed. It has a unique design with the ability to insert ppm amounts of media into a hot air flow, in order to simulate different environmental changes, e.g. varying amount and composition of combustion residue particles.

    PVD coated valves were evaluated in a dry atmosphere. It was concluded that although some of the coatings showed potential, the substrate could not support the thin, hard coatings.

    Investigations with an addition of different oils have been performed. Fully formulated oils proved to build up a protective oil residue tribofilm. This tribofilm has been in-depth analysed and proved to have similar composition and appearance as tribofilms found on low wear field tested valves. With a non-additivated oil, wear particles from the valve seat insert formed a wear particle tribofilm on top of the valve sealing surface. Without any oil the surfaces showed severe wear with wear particles spread over the surfaces.

    The results presented give a hint about what to be expected in the future, when the engine oils are replaced with ash less oils with reduced amount of additives and the consumed amount of oil within the cylinders are reduced. 

    List of papers
    1. Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations
    Open this publication in new window or tab >>Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations
    2014 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 150-155Article in journal (Refereed) Published
    Abstract [en]

    The rapid sharpening of the environmental legislation during the last decades has forced engine manufacturers to radical design modifications. It has been shown that the sliding in the sealing interface is one of the major reasons for wear. The sliding wear is expected to have an even more important role in modern engines. This paper presents unique experimental data, acquired using a dedicated technique in a test-rig. The experimental data is complemented by FEM-simulations. The simulations involve validation of the test-rig valve sealing interface sliding behaviour and investigations on how different parameters influence the sliding length. These parameters include combustion pressure, contact angle, contact length, valve head thickness, coefficient of friction, running-in wear, and change of elastic modulus due to temperature variations.

    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-204452 (URN)10.1016/j.triboint.2013.09.014 (DOI)000328183100017 ()
    Available from: 2013-08-05 Created: 2013-08-05 Last updated: 2018-01-11Bibliographically approved
    2. Wear mechanism study of exhaust valve system in modern heavy duty combustion engines
    Open this publication in new window or tab >>Wear mechanism study of exhaust valve system in modern heavy duty combustion engines
    2011 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 271, no 9-10, p. 2477-2484Article in journal (Refereed) Published
    Abstract [en]

    The increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of soot which can build up a protective film are some of the increasing challenges which the system has to endure.

    Three pairs of valves and valve seat inserts with the same material and design properties but with different service condition have been analyzed with a variety of analytical instruments to gain information of how the wear occurs.

    The wear mechanisms found were a combination of oxidation, where many different oxides were found, adhesive wear, which was seen both in form of material transfer and flow lines. On top of Sample Mild and Hard there were tribo films of thickness varying from 1 to 5 mu m consisting of Ca, O, P, S and Zn. The film has in all cases protected the underlying surface from wear but in some cases seems to have a corrosive impact instead.

    Keywords
    Exhaust valve system, Wear, Oxidative, Corrosive, Adhesive
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-162392 (URN)10.1016/j.wear.2010.11.039 (DOI)000294590200162 ()
    Available from: 2011-11-30 Created: 2011-11-30 Last updated: 2017-12-08Bibliographically approved
    3. Combustion valve simulation rig with particle flow
    Open this publication in new window or tab >>Combustion valve simulation rig with particle flow
    (English)In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833Article in journal (Refereed) Submitted
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Identifiers
    urn:nbn:se:uu:diva-201863 (URN)
    Available from: 2013-06-17 Created: 2013-06-17 Last updated: 2018-01-11Bibliographically approved
    4. Wear study of coated heavy duty exhaust valve systems in a experimental test rig
    Open this publication in new window or tab >>Wear study of coated heavy duty exhaust valve systems in a experimental test rig
    2012 (English)In: SAE International technical papersArticle in journal (Refereed) Published
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-173681 (URN)10.4271/2012-01-0546 (DOI)
    Available from: 2012-05-02 Created: 2012-05-02 Last updated: 2018-01-12Bibliographically approved
    5. Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig
    Open this publication in new window or tab >>Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig
    2013 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, p. 1351-1359Article in journal (Refereed) Published
    Abstract [en]

    Increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of particulates which can build up a protective film are some of the increasing challenges which the system has to endure. Thick protective tribofilms found on heavy duty exhaust valve surfaces have been analysed with SEM, TEM, EFTEM, STEM-EDS, Nano-indenter and XPS in order to get a better understanding for the tribofilms properties. Two analysed samples are presented in this paper, from a field service truck and another from atest rig which uses vaporised engine oil to simulate the particle flow. The tribofilms are built upfrom several layers with varying compositions. Most of the material originates from oil additives, but also metallic oxides and other carbon compounds produced in the combustion system. The similarities between the rig generated tribofilm and the tribofilm found on the field tested valve verify the test rig behaviour and opens up for realistic wear testing where the importance ofthe protective tribofilm can be investigated in detail that is not possible in motor tests. 

    Place, publisher, year, edition, pages
    Elsevier, 2013
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials
    Identifiers
    urn:nbn:se:uu:diva-201859 (URN)10.1016/j.wear.2013.01.061 (DOI)000322682800058 ()
    Available from: 2013-06-17 Created: 2013-06-17 Last updated: 2018-01-11Bibliographically approved
    6. The importance of oil and particle flow for exhaust valve wear - An experimental study
    Open this publication in new window or tab >>The importance of oil and particle flow for exhaust valve wear - An experimental study
    2014 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 176-183Article in journal (Refereed) Published
    Abstract [en]

    Oil residue particles have a large impact in protecting the sealing surfaces of heavy duty exhaust valves. To increase the understanding of the mechanism behind this, the wear behavior of exhaust valves subjected to a flow of hot air with controlled amounts of oil particles of three different compositions has been investigated. Air flow without addition of oil was used as a reference. The degree and mechanisms of surface damage proved to be sensitive to the test parameters. Residues from the oils containing additives proved to form protective tribofilms, while the oil without additives promoted agglomeration of wear debris on the sealing surfaces. The dry reference showed severe wear with debris scattered over the surfaces.

    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Research subject
    Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-204467 (URN)10.1016/j.triboint.2013.09.009 (DOI)000328183100020 ()
    Available from: 2013-08-06 Created: 2013-08-06 Last updated: 2019-09-16
  • 9.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Debord, Dominique
    Scania CV AB.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Quantification of Combustion Valve Sealing Interface Sliding - A Novel Experimental Technique and Simulations2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 150-155Article in journal (Refereed)
    Abstract [en]

    The rapid sharpening of the environmental legislation during the last decades has forced engine manufacturers to radical design modifications. It has been shown that the sliding in the sealing interface is one of the major reasons for wear. The sliding wear is expected to have an even more important role in modern engines. This paper presents unique experimental data, acquired using a dedicated technique in a test-rig. The experimental data is complemented by FEM-simulations. The simulations involve validation of the test-rig valve sealing interface sliding behaviour and investigations on how different parameters influence the sliding length. These parameters include combustion pressure, contact angle, contact length, valve head thickness, coefficient of friction, running-in wear, and change of elastic modulus due to temperature variations.

  • 10.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Elo, Robin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The importance of oil and particle flow for exhaust valve wear - An experimental study2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 69, p. 176-183Article in journal (Refereed)
    Abstract [en]

    Oil residue particles have a large impact in protecting the sealing surfaces of heavy duty exhaust valves. To increase the understanding of the mechanism behind this, the wear behavior of exhaust valves subjected to a flow of hot air with controlled amounts of oil particles of three different compositions has been investigated. Air flow without addition of oil was used as a reference. The degree and mechanisms of surface damage proved to be sensitive to the test parameters. Residues from the oils containing additives proved to form protective tribofilms, while the oil without additives promoted agglomeration of wear debris on the sealing surfaces. The dry reference showed severe wear with debris scattered over the surfaces.

  • 11.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig2013Conference paper (Refereed)
    Abstract [en]

    Increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of particulates which can build up a protective film are some of the increasing challenges which the system has to endure. Thick protective tribofilms found on heavy duty exhaust valve surfaces have been analysed with SEM, TEM, EFTEM, STEM-EDS, Nano-indenter and XPS in order to get a better understanding for the tribofilms properties. Two analysed samples are presented in this paper, from a field service truck and another from atest rig which uses vaporised engine oil to simulate the particle flow. The tribofilms are built upfrom several layers with varying compositions. Most of the material originates from oil additives, but also metallic oxides and other carbon compounds produced in the combustion system. The similarities between the rig generated tribofilm and the tribofilm found on the field tested valve verify the test rig behaviour and opens up for realistic wear testing where the importance ofthe protective tribofilm can be investigated in detail that is not possible in motor tests. 

  • 12.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Comparison and analysis of protective tribofilms found on heavy duty exhaust valves from field service and made in test rig2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, p. 1351-1359Article in journal (Refereed)
    Abstract [en]

    Increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of particulates which can build up a protective film are some of the increasing challenges which the system has to endure. Thick protective tribofilms found on heavy duty exhaust valve surfaces have been analysed with SEM, TEM, EFTEM, STEM-EDS, Nano-indenter and XPS in order to get a better understanding for the tribofilms properties. Two analysed samples are presented in this paper, from a field service truck and another from atest rig which uses vaporised engine oil to simulate the particle flow. The tribofilms are built upfrom several layers with varying compositions. Most of the material originates from oil additives, but also metallic oxides and other carbon compounds produced in the combustion system. The similarities between the rig generated tribofilm and the tribofilm found on the field tested valve verify the test rig behaviour and opens up for realistic wear testing where the importance ofthe protective tribofilm can be investigated in detail that is not possible in motor tests. 

  • 13.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hieke, André
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Performance of DLC coatings in heated commercial engine oil2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 304, no 1-2, p. 211-222Article in journal (Refereed)
    Abstract [en]

    Multilayer Diamond Like Coatings (DLC) are widely used to protect highly loaded components from wear and/or to reduce the friction losses in combustion engines. The uppermost layer of the coating controls the chemical situation in the contact and is therefore a very important part of modern multilayer coatings. To examine the individual performances and assess differences and potentials of modern DLC coatings, four commercially available DLCs designed for automotive components with different doping elements together with an uncoated reference were tested in high performance engine oils heated to 90 °C at two different initial contact pressures. The coefficient of friction generally was higher in the tests with the lower initial contact pressure (approximately 20% for all combinations) and the specific wear rate was also up to 100% higher for some combinations. It was also found that a used motor oil showed up to 30% higher friction than when fresh and at the same time reduced the wear in most cases. The tungsten doped coating showed the highest wear, but also the lowest coefficient of friction. The Si doped coating showed the best wear results, most probably due to the ability to make use of the additives in the oil to form a protecting tribofilm.

  • 14.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Combustion valve simulation rig with particle flowIn: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833Article in journal (Refereed)
  • 15.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Heavy duty exhaust valve simulation and evaluation in a test rig2012In: Nordtrib, Trondheim, 2012, 2012Conference paper (Refereed)
  • 16.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Protective tribofilm build up from exhaust residues on the surface on  exhaust valve systems in a test rig2012In: Nordtrib, Trondheim, Norway, 2012, 2012Conference paper (Refereed)
  • 17.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear study of coated heavy duty exhaust valve systems in a experimental test rig2012Conference paper (Refereed)
  • 18.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear study of coated heavy duty exhaust valve systems in a experimental test rig2012In: SAE International technical papersArticle in journal (Refereed)
  • 19.
    Forsberg, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hollman, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The Uppsala Load Scanner –Second generation2010In: Nordtrib 2010, Storforsen, Sweden, 2010Conference paper (Other academic)
  • 20.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Friction and wear behaviour of low-friction coatings in conventional and alternative fuels2012In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 48, p. 22-28Article in journal (Refereed)
    Abstract [en]

    Today low-friction PVD coatings are used regularly in combustion engines to reduce wear and energy loss due to friction. Three coatings based on transition-metal dichalcogenides and three DLC coatings were tested with respect to tribological behaviour in non-conformal sliding contact, in five conventional and alternative fuels and fuel blending components. The friction and wear proved to vary substantially between the different tested systems. The DLC coatings exhibited extremely good wear properties, but also higher friction. Contrastingly the TMD coatings showed promising friction results, but in their present forms they do not offer sufficient wear resistance in the tested severe contact situation.

  • 21.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Investigations of the friction behaviour and surface modifications for low-friction coatings in traditional and new alternative fuels2010In: NordTrib 2010, 2010Conference paper (Refereed)
  • 22.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hieke, André
    Ionbond Netherlands.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    How tribological propertiesof DLC coatings vary in different engine oils at elevated temperature2012In: Nordtrib, Trondheim, Norge, 2012Conference paper (Refereed)
    Abstract [en]

    Improving fuel economy and tribological properties in automotive applications is a continuous quest, where only a few percent decrease in friction and emissions can make a huge difference. Energy savings and environmental influence are today very important factors when designing new tribological systems for automotive applications.

    DLC coatings are often seen as a homogenous group of hard amorphous carbon coatings, being chemically inert with great wear resistance in most lubricated environments. However, the hardness can vary within almost an order of magnitude between different DLC variants and combined with large variations in chemical composition, the wear and friction properties may vary significantly, depending on the test conditions.

    In this study, an experimental coating of amorphous carbon deposited with PA-CVD is compared with three commercially available and optimized DLC coatings, frequently used in automotive applications. The coatings have different hardness, chemical composition and structure.

    The coatings are tested in a reciprocal sliding test rig, at contact pressures and temperature representative of real engines. The tests are performed at low speeds and are designed to operate in the boundary friction regime, where the need for coatings is the highest. An uncoated reference material is tested with the same parameters to highlight the benefits of the coatings under the different test conditions. Five oils are tested, including four special oils designed with different amounts of additives and one used dully formulated engine oil taken from a real engine.

    Results show that the DLCs do not behave as a homogenous group, but have different tribological properties depending on the hardness and composition. Interestingly, the ranking of the coatings varies for the different oils. Special attention is put on friction and wear behavior and on how the surfaces have changed during the test. Further, deeper surface analysis of some selected systems is performed using EDS, XPS and TEM.

  • 23.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Renman, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Formation of tribologically beneficial layer on counter surface with smart chemical design of DLC coating in fuel contact2012In: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 6, no 3, p. 102-108Article in journal (Refereed)
  • 24.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    All roads lead to Rome: On the numerous routes to low-friction WS2 tribofilms2013Conference paper (Refereed)
  • 25.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Cavaleiro, Albano
    Polcar, Tomas
    Frictional behavior of self-adaptive nanostructural Mo-Se-C coatings in different sliding conditions2013In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 303, no 1-2, p. 286-296Article in journal (Refereed)
    Abstract [en]

    Sliding properties of Mo-Se-C coatings with two different carbon content deposited by magnetron sputtering were investigated in different sliding environments (argon, nitrogen, dry and humid air). Both coatings had a structure that was identified as randomly oriented structures of MoSe2 embedded into amorphous carbon matrix. The worn surfaces, i.e. the wear tracks and the wear scars of the balls, were analyzed by optical microscopy, Raman spectroscopy and scanning electron microscopy. The material transferred to the ball steel surfaces was almost exclusively MoSe2, whereas the wear tracks on the coatings were more complex, with areas rich in MoSe2 and areas similar to that of as-deposited coatings. The friction was lowest in argon (0.012 at a load of 10 N) and highest in humid air, but still remarkably low; as best 0.05 at 10 N load; however, the exceptionally low wear rate was almost identical. Thus, we focused our detailed analysis on these two examples to understand the mechanisms responsible for the difference between the friction coefficients. SEM, EDX, XPS, Raman and TEM with EELS and EDX were applied to investigate the composition and structure of localized spots of interest on the tested surfaces. In both cases, we observed well-ordered MoSe2 tribofilms with negligible amount of oxides. Carbon was not present in the sliding interfaces, although large amount of carbon was found outside the contacts on both surfaces. Based on our investigations, we suggest the increase in friction of Mg-Se-C in humid air is primarily due to the increase in shear strength of the MoSe2 structure by the presence of water molecules in the sliding interface

  • 26.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Cavaleiro, Albano
    Polcar, Tomas
    Ultra-low friction of W-S-N solid lubricant coating2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 232, p. 541-548Article in journal (Refereed)
    Abstract [en]

    W-S-N films were deposited by reactive magnetron sputtering from WS2 target in Ar/N-2 atmosphere. Besides the standard evaluation of composition, structure, morphology, hardness and cohesion/adhesion, the core objective of this paper was to analyze coating tribological behavior. The chemical composition was 34 at.%N, 12 at%O, 29 at.%W and 25 at.%S, and the as-deposited films were completely amorphous. The film thickness was 23 pm, including the approximately 300-nm thick adhesion improving titanium interlayer. The friction coefficient was lower than 0.003 when sliding in dry nitrogen. The coating showed remarkable wear resistance surviving more than 2 million laps on pin-on-dics. The excellent friction properties were attributed to the formation of a thin tungsten disulfide tribofilm on the top of the wear track of the coating and on the counterpart surface. Moreover, the coating showed ability to replenish damaged areas with solid lubricant. We demonstrated that a structural transformation of the coating from an amorphous-like to a gradient quasi-ordered structure and an ordered transfer layer formation improved mechanical properties and radically decreased friction and wear.

  • 27.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Polcar, Tomas
    Cavaleiro, Albano
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hard low friction WSN coating deposited by magnetron sputtering: Sliding in dry nitrogen2011Conference paper (Refereed)
  • 28.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Polcar, Tomas
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Cavaleiro, Albano
    Tribology of selenium-based solid lubricants alloyed with carbon2012In: Advances in lubrication, Costa Rica, 2012Conference paper (Refereed)
  • 29.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svahn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bexell, Ulf
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nanoparticle based and sputtered WS2 low-friction coatings - Differences and similarities with respect to friction mechanisms and tribofilm formation2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 232, p. 616-626Article in journal (Refereed)
    Abstract [en]

    MoS2 and WS2 are widely known intrinsic low-friction materials that have been extensively used and thoroughly investigated in literature. They are commonly produced in the form of sputtered coatings and show extremely low friction coefficients in non-humid environments, but rapidly degrade in humid conditions. Close nested fullerene-like nanoparticles of these materials have been proposed to have better oxidation resistance due to their closed form with the absence of dangling bonds. In the present study, an electrochemically deposited coating consisting of fullerene-like nanoparticles of WS2 embedded in a Ni-P matrix is tested under various loads and humidity conditions and compared with a sputtered WS2 coating with respect to their tribological behavior. The formation of a tribofilm on both surfaces is known to be crucial for the low-friction mechanism of WS2 and the different mechanisms behind this formation for the two types of coatings are investigated. It is shown that despite the completely different transformation processes, the resulting tribofilms are very similar. This is analyzed thoroughly using SEM, AES and TEM. The friction coefficient is known to be lower at higher normal loads for these materials and in the present study the mechanical and chemical responses of the tribofilm to higher normal loads during sliding are investigated. It was observed that the basal planes become aligned more parallel to the surface at higher loads, and that the tribofilm is less oxidized. It is suggested that these mechanisms are connected and are crucial keys to the wear life of these materials.

  • 30.
    Hassila Karlsson, Carl Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribological testing of top hammer drill buttons2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the present work further modifications are implemented to an existing test setup for the evaluation of the wear of cemented carbide drill buttons in rock drilling applications. The test setup has been evaluated in previous diploma works, which has shown that the test successfully mimics the wear seen in rock drilling applications. The new modifications include friction and normal force measurements together with the collection of rock debris. This has been made possible by redesigning the sample holder and by manufacturing equipment making rock debris collection possible. The new modifications to the test setup were evaluated by comparing the wear of three different cemented carbide grades tested against sandstone and granite with two different loads.

    The data collected from the new modifications were found to be robust with lower than expected spread of data. The coefficient of friction when testing against sandstone was higher than when testing against granite. More adhered material was observed on the wear surface when testing against granite than against sandstone. Load dependence on the wear of the cemented carbide buttons is only seen for the softer cemented carbide grades when testing against sandstone. The wear of the buttons indicates a high dependence on the hardness of the different grades as shouldbe expected. This diploma work has been performed for Sandvik Mining, Rock Tools,a world leading supplier of rock drill equipment.

  • 31.
    Heinrichs, Jannica
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kawakami, Ayumi
    YKK Corporation, Japan.
    Mikado, Hiroko
    YKK Corporation, Japan.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kawamura, Shingo
    YKK Corporation, Japan.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear mechanisms of WC-Co cemented carbide tools and PVD coated tools used for shearing Cu-alloy wire2018Conference paper (Other academic)
  • 32.
    Heinrichs, Jannica
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Olsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Materials Science, Dalarna University, Sweden.
    Almqvist, Bjarne
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Initial surface failure and wear of cemented carbides in sliding contact with different rock types2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 408-409, p. 43-55Article in journal (Refereed)
    Abstract [en]

    The initial wear, deformation and degradation of cemented carbide in contact with different rock types are studied using a crossed cylinder sliding test. The sliding distance is limited to centimetres at a time, interrupted by successive SEM analysis. This allows for careful studies of the gradually changing microstructure of the cemented carbide during the test. Five different rock types are included; granite, metal sulphide ore, mica schist, quartzite and marble. All rock types are very different in microstructure, composition and properties. The cemented carbide grade used for the evaluation contains 6 wt% Co and fine (~ 1 µm) WC grains, a grade commonly used in rock drilling. The results show that the cemented carbide microstructure becomes altered already during the very first contact with rock. The initial wear rate and wear character is highly influenced by the rock type. The initial wear of the cemented carbide is highest against quartzite and lowest against marble.

  • 33.
    Heldin, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Designing grinding tools to control and understand fibre release in groundwood pulping2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mechanical pulping is a very energy demanding process in which only a fraction of the energy is used for the actual separation of wood fibres. The rest of the energy is lost, partly in damaging already separated fibres and partly as heat during viscoelastic deformation of the wood. Groundwood pulping is one of the major mechanical pulping processes. In this process, a piece of wood is pressed against a rotating grinding stone. The stone surface has traditionally been made of grinding particles fused to a vitrified matrix. Though the process is close to 200 years old, the detailed mechanisms of the interactions between the grinding particles and the wood surface are still not fully understood. The random nature of the grinding stones combined with the heterogeneous nature of wood creates a stochastic process that is difficult to study in detail. This work utilizes well-defined tools, that facilitate testing and analysis, to increase the understanding of the tool-wood-interaction. In-situ tomography experiments were performed with such well-defined tools, to study the deformations and strains induced in the wood as the tool asperities engage the wood surface. Numerical simulations were used to study the influence of asperity shape, and to show how the induced strains promote intercellular cracks and fibre separation. Several well-defined tool surfaces were designed and tested in a newly developed lab-scale grinding equipment, to study their performance in terms of energy consumption and the quality of the produced fibres. It was shown that the well-defined grinding surfaces, with asperities the same size as a fibre diameter, can be designed both to achieve drastically lower energy consumption compared with that of traditional stones and to produce long and undamaged fibres. This thesis shows that it is possible to design future tools that can help reducing the energy consumption in industrial pulping.

    List of papers
    1. Initiation of wood defibration in groundwood pulping, single asperity indentation and scratching
    Open this publication in new window or tab >>Initiation of wood defibration in groundwood pulping, single asperity indentation and scratching
    2016 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 3, p. 401-406Article in journal (Refereed) Published
    Abstract [en]

    To understand how the energy requirements of the mechanical pulping process can be reduced, the fundamental mechanisms behind fiber separation in Norway spruce were studied experimentally and analytically. Single tip scratching in heated water was used to reproduce initial defibration mechanisms found industrially. The resulting scratches were then compared with surfaces ground in a real industrial process. Moreover, the mechanical behavior of the wood microstructure was monitored with X-ray computed microtomography as a single hard tip was pressed into it. Subsequent digital image correlation was applied to estimate the strain field in the region around the indenting tip. Regions in the wood with high tensile or shear strains were identified, i.e. where cracking and fiber separation is believed to initiate.

    Keywords
    Defibration, Scratching, Strain analysis
    National Category
    Engineering and Technology Wood Science
    Research subject
    Engineering Science with specialization in Tribo Materials
    Identifiers
    urn:nbn:se:uu:diva-310478 (URN)000387974800001 ()
    Funder
    Swedish Energy Agency
    Available from: 2016-12-16 Created: 2016-12-16 Last updated: 2019-05-02Bibliographically approved
    2. Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale
    Open this publication in new window or tab >>Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale
    2019 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed) Epub ahead of print
    Abstract [en]

    With industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.

    Keywords
    CT; Defibration; DVC; FE; Grinding; Wood
    National Category
    Paper, Pulp and Fiber Technology Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
    Identifiers
    urn:nbn:se:uu:diva-382716 (URN)
    Funder
    Swedish Energy Agency, 37206-2
    Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-11-20
    3. Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools
    Open this publication in new window or tab >>Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools
    2019 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Groundwood pulping is a process that employs large machines, making them difficult to use in research. Lab scale grinders exist, but even though they are smaller, the sizes of the grinding stones or segments make them cumbersome to exchange and tailor. This study presents a method and an apparatus for investigating the detailed mechanisms and the energy requirements behind the fibre separation process. A well-defined grinding tool was used at three different temperatures to demonstrate that the equipment can differentiate levels of energy consumption and defibration rates, confirming the well-known fact that a higher temperature facilitates defibration. It is also shown how the equipment can be used to study the influence of grinding parameters, exemplified by the effect of temperature on the way fibres are separated and the character of the produced fibres. A key feature of the equipment is the use and evaluation of small grinding surfaces, more readily designed, produced, evaluated and studied. This reduces both the cost and time necessary for testing and evaluating. At the same time, a technique to produce well defined grinding surfaces was employed, which is necessary for repeatability and robust testing, not achievable with traditional grinding stones.

    Keywords
    Computed tomography, Energy efficiency, Groundwood pulping, Lab scale equipment, Test method
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Paper, Pulp and Fiber Technology
    Identifiers
    urn:nbn:se:uu:diva-382698 (URN)10.1515/npprj-2019-0063 (DOI)
    Funder
    Swedish Energy Agency, 37206-2
    Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2020-02-19Bibliographically approved
    4. Influences of load and temperature on groundwood pulping with well-defined tools
    Open this publication in new window or tab >>Influences of load and temperature on groundwood pulping with well-defined tools
    2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 438-439, article id 203051Article in journal (Refereed) Published
    Abstract [en]

    Groundwood pulping is an industrial process with a high energy demand, although only a minor part of the energy is used for actually separating the fibres and the rest for working them. Traditionally, the separation process employs a grinding stone having particles embedded in a softer matrix. The position and distribution of the particles have been random, causing their interaction with the wood to also be random. This makes studies of the mechanisms during the separation process difficult. Knowledge of the mechanisms in the separation process helps when designing future tools aimed at energy efficiency or tailored fibre properties. Recently, grinding surfaces having diamond particles brazed to a steel backing at fixed positions have been developed and commercialised. In this work, individual particles are not positioned at the tool surfaces. Instead, well-defined structured diamond films, soldered to a backing, are used as grinding tools. The grinding asperities of such films can be tailored to shapes that are not possible to achieve by using particles. Using this kind of tool in a lab scale grinding equipment, confirms the well-known fact that increased load or increased temperature both lead to lower energy consumption for fibre separation and longer, less damaged fibres.

    Place, publisher, year, edition, pages
    Elsevier, 2019
    Keywords
    Grinding, Pulping, Wood tomography, Energy savings, Tool design
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Paper, Pulp and Fiber Technology
    Identifiers
    urn:nbn:se:uu:diva-382700 (URN)10.1016/j.wear.2019.203051 (DOI)000500939900018 ()
    Funder
    Swedish Energy Agency, 37206-2
    Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2020-01-14Bibliographically approved
    5. Evaluation of well-defined tool surface designs for groundwood pulping
    Open this publication in new window or tab >>Evaluation of well-defined tool surface designs for groundwood pulping
    2019 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 4, p. 9575-9587Article in journal (Refereed) Published
    Abstract [en]

    Groundwood pulping is a process in which logs are pressed against a rotating grinding stone. A conventional grinding stone is generally made of grinding particles in a vitrified matrix. As the particles are practically round, their contact with the wood is limited to occasional point contacts. The interaction between the particles and the wood occurs at random positions and at random times, only intermittently contributing to the defibration process. In this work, well-defined grinding tools with asperities giving line contacts rather than point contacts were tested. The tool surface asperities were elongated in shape and positioned with different density over the surface. The tools were tested in a lab-scale equipment at elevated temperatures, and their performance was compared to that of a conventional grinding stone. The grinding mechanisms varied between the different tools, and the specific grinding energy was reduced compared to the conventional tool.

    Keywords
    Groundwood pulping, Diamond tools, Energy consumption, Tomography, Grinding mechanisms
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Paper, Pulp and Fiber Technology
    Identifiers
    urn:nbn:se:uu:diva-382701 (URN)10.15376/biores.14.4.9575-9587 (DOI)000493997400141 ()
    Funder
    Swedish Energy Agency, 37206-2
    Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-12-05Bibliographically approved
    6. Influence of alignment between extended tool ridges and the wood structure on the defibration mechanisms in groundwood pulping experiments
    Open this publication in new window or tab >>Influence of alignment between extended tool ridges and the wood structure on the defibration mechanisms in groundwood pulping experiments
    (English)Manuscript (preprint) (Other academic)
    National Category
    Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Paper, Pulp and Fiber Technology
    Identifiers
    urn:nbn:se:uu:diva-382709 (URN)
    Funder
    Swedish Energy Agency, 37206-2
    Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-09-10
  • 34.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Carlsson, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On tool engagement in groundwood pulping - in-situ observations and numerical modelling at the microscale2019In: The 11th Fundamental Mechanical Pulp Research Seminar, Norrköping, Sweden, April 2-4, 2019Conference paper (Other academic)
  • 35.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A labscale test equipment ot study the tool surface influence in pressure groundwood pulping2015In: 20th International Conference on Wear of Materials, Toronto, Canada, April 12-16, 2015Conference paper (Other academic)
    Abstract [en]

    A test rig has been designed to allow controlled studies of the mechanisms in the industrial Pressure Ground Wood (PGW) pulping process:

    • The equipment consists of a setup similar to a lathe, with a tool sliding against a rotation wood workpiece.
    • Placed inside a pressure chamber which allows testing at steam temperatures and pressures exceesing those in industrial pulping.
    • Normal force and friction force are continuously monitored.
    • Separated fibers, collected after the test, the tool surface and the track of the machined workpiece are analysed after the test.
  • 36.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools2019In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Article in journal (Refereed)
    Abstract [en]

    Groundwood pulping is a process that employs large machines, making them difficult to use in research. Lab scale grinders exist, but even though they are smaller, the sizes of the grinding stones or segments make them cumbersome to exchange and tailor. This study presents a method and an apparatus for investigating the detailed mechanisms and the energy requirements behind the fibre separation process. A well-defined grinding tool was used at three different temperatures to demonstrate that the equipment can differentiate levels of energy consumption and defibration rates, confirming the well-known fact that a higher temperature facilitates defibration. It is also shown how the equipment can be used to study the influence of grinding parameters, exemplified by the effect of temperature on the way fibres are separated and the character of the produced fibres. A key feature of the equipment is the use and evaluation of small grinding surfaces, more readily designed, produced, evaluated and studied. This reduces both the cost and time necessary for testing and evaluating. At the same time, a technique to produce well defined grinding surfaces was employed, which is necessary for repeatability and robust testing, not achievable with traditional grinding stones.

  • 37.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Designed tools for controlling the defibration mechanisms in the pressure groundwood process2015In: International Tribology Conference, Tokyo 2015, Tokyo, Japan, September 16-20, 2015Conference paper (Other academic)
    Abstract [en]

    The pulp and paper industry is a large global industry producing millions of tons of paper each year. To produce pulp for this paper, only a handful of processes are used. One of these is the mechanical pulping process, called Pressure Ground Wood (PGW). Although commonly used, the tribological details of the mechanisms behind the stochastic fiber separation are not well known.

    In order to study these mechanisms, and the influence of geometries at the tool surface, a test equipment allowing testing in a similar, but more controlled, environment is needed. For this purpose, a lab scale rig has been designed, capable of grinding at temperatures and pressures at industrially relevant conditions. The tools used are made of CVD-diamond thin films, structured into different well defined patterns of sharp edges. Samples of Norway spruce have been ground both using these tools and a conventional grinding stone surface. The fibers produces are compared and the possibility of controlling the fiber characteristics using the designed tools is discussed.

  • 38.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Evaluation of well-defined tool surface designs for groundwood pulping2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 4, p. 9575-9587Article in journal (Refereed)
    Abstract [en]

    Groundwood pulping is a process in which logs are pressed against a rotating grinding stone. A conventional grinding stone is generally made of grinding particles in a vitrified matrix. As the particles are practically round, their contact with the wood is limited to occasional point contacts. The interaction between the particles and the wood occurs at random positions and at random times, only intermittently contributing to the defibration process. In this work, well-defined grinding tools with asperities giving line contacts rather than point contacts were tested. The tool surface asperities were elongated in shape and positioned with different density over the surface. The tools were tested in a lab-scale equipment at elevated temperatures, and their performance was compared to that of a conventional grinding stone. The grinding mechanisms varied between the different tools, and the specific grinding energy was reduced compared to the conventional tool.

  • 39.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of alignment between extended tool ridges and the wood structure on the defibration mechanisms in groundwood pulping experimentsManuscript (preprint) (Other academic)
  • 40.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influences of grinding surface alignment in groundwood pulping of Norway spruce2018In: 18th Nordic Symposium on Tribology - NORDTRIB 2018, Uppsala, Sweden, June 18-21, 2018Conference paper (Other academic)
  • 41.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influences of load and temperature on groundwood pulping with well-defined tools2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 438-439, article id 203051Article in journal (Refereed)
    Abstract [en]

    Groundwood pulping is an industrial process with a high energy demand, although only a minor part of the energy is used for actually separating the fibres and the rest for working them. Traditionally, the separation process employs a grinding stone having particles embedded in a softer matrix. The position and distribution of the particles have been random, causing their interaction with the wood to also be random. This makes studies of the mechanisms during the separation process difficult. Knowledge of the mechanisms in the separation process helps when designing future tools aimed at energy efficiency or tailored fibre properties. Recently, grinding surfaces having diamond particles brazed to a steel backing at fixed positions have been developed and commercialised. In this work, individual particles are not positioned at the tool surfaces. Instead, well-defined structured diamond films, soldered to a backing, are used as grinding tools. The grinding asperities of such films can be tailored to shapes that are not possible to achieve by using particles. Using this kind of tool in a lab scale grinding equipment, confirms the well-known fact that increased load or increased temperature both lead to lower energy consumption for fibre separation and longer, less damaged fibres.

  • 42.
    Heldin, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tailored grinding surfaces for groundwood pulping - influencing wear mechanisms and energy requirements2017In: 21st International Conference on Wear of Materials, Long Beach, March 26-30, 2017Conference paper (Other academic)
  • 43.
    Hogmark, Sture
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Sturesson, Peter
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    On the mechanisms of friction between skis and snow and implications on how to prepare the skis for optimum glide2008Conference paper (Refereed)
  • 44.
    Holmberg, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Andersson, Michael
    Hoganas AB, Bruksgatan 35, SE-26383 Hoganas, Sweden.
    Kassman Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Rolling fatigue life of PM steel with different porosity and surface finish2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 426-427, no Part A, p. 454-461Article in journal (Refereed)
    Abstract [en]

    Gears made of PM steel are of interest for the automotive industry because they can be produced to near net shape with only a few processing steps. Automotive gears experience a complex contact situation with rolling as well as combined rolling and sliding. They also have to be able to withstand high loads and fairly high temperature variations. Earlier work show that the main limiting parameter of the contact fatigue life of PM steel is the porosity. A higher porosity/lower density will decrease the fatigue life of the PM component. In the present study, the pure rolling contact fatigue life of PM steel with different density and surface finish has been investigated. A rolling contact fatigue test rig, where rods of the tested material are mounted between two rolling wheels, was used. Two densities of PM steel, 6.8 and 7.15 g/cm(3) and a full density reference steel with two different surface finishes, centerless grinded and superfinished, were tested. The tests were run for a given number of load cycles or until failure (fatigue life). SEM was used to study the surfaces and cross-sections to reveal the mechanisms of crack initiation and propagation. The higher density PM steel (7.15 g/cm(3)) outperformed the lower density steel (6.18 g/cm(3)) by a factor of around 4 in fatigue life at the same surface pressure, regardless of surface finish. Cracks are initiated at a depth of around 100 mu m. These cracks propagate and eventually they reach the surface, causing surface damage and failure. For the low density PM steel, both sub surface crack initiation and failure occurred earlier (at a lower number of load cycles) than for the higher density PM steel. Severe surface damage or wear were not found until failure occurred. Still, some initial alteration of the surfaces was seen already after 0.5 million load cycles, in the form of removal of the highest asperity peaks on the centerless grinded surfaces, and opening of the surface pores on the superfinished surface. No effect of surface finish was found on the fatigue life. The difference in surface roughness could induce a difference in local stress concentrations at the surface, but in this test the cracks causing fatigue failure are initiated at a depth where the stress distribution is not affected by local surface stress concentrations. This means that for fairly smooth surfaces roughness, the surface of PM steel is not important when it comes to pure rolling fatigue life.

  • 45.
    Jacobson, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wear and degradation of Co, Fe and Ni-based cemented carbides against sandstone and granite2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This diploma work is performed at Sandvik Mining and Rock Technology, Rock Tools division, a world-leading mining equipment manufacturer. The aim is to study the wear of cemented carbide rock drill inserts worn against granite and sandstone countersurfaces, with focus on the impact of binder phase composition and flushing agent chemistry. A brief introduction to rock drilling, cemented carbides and the wear and degradation mechanisms of cemented carbides in rock drilling is given.

    Wear is induced in a lab test by sliding cemented carbide inserts against granite and sandstone countersurfaces while flushing with deionized water or synthetic mine water. The wear is quantified by measuring material weight loss, and worn inserts are studied by SEM.

    All wear marks feature crushed, fragmented and heavily deformed WC grains and cavities left after individually removed WC grains. Rock adhere strongly on inserts worn against both granite and sandstone, and adhered material from both rock types sometimes endure the mechanical contact between insert and rock without significant spalling. Inserts tested with deionized water against sandstone wear 2.2 - 5.1 times more relative to against granite, and the only distinct difference observed is the distribution of adhered rock. The use of synthetic mine water relative to deionized water impacts the wear of all inserts, though corrosion products are only found on some of them. Further, the tribological contact greatly impacts the corrosive attack. The relative wear difference using different water chemistries is larger for inserts with a smaller relative amount of binder. In most cases, increased wear is measured for inserts tested with synthetic mine water. For reasons yet unknown, this trend is reversed for inserts with a high relative amount of binder tested against sandstone, where a decrease in wear is measured instead.

  • 46.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Coatings and surface treatments: interaction with lubricants2012In: The Handbook of Lubrication and Tribology: Volume II: Theory and Design, Second Edition / [ed] R W Bruce, CRC Press, 2012, p. 41-1-41-13Chapter in book (Refereed)
  • 47.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Friction in curling –Fundamentals and applications of friction on ice illustrated by the Olympic winter sport: Keynote Talk2015Conference paper (Refereed)
  • 48.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Low-friction Sliding Without Lubrication– Five Working Material Concepts and Tribological Challenges2014Conference paper (Refereed)
    Abstract [en]

    Low-friction sliding without lubrication – five working material concepts and tribological challenges

    The most fundamental rule for achieving low-friction sliding is to keep the area of contact small and the shear stress low. Of course, this beneficial combination is most often realised by using hard contacting materials and adding a lubricant. However, in some cases fluid lubricants are undesirable, and in others they may temporarily or locally be missing even when intended to be present.

    In the absence of a lubricant, the combined requirements of small contact area and low shear stress poses contradicting demands on the contacting materials. A small contact area requires a hard material (i.e. hard to deform plastically) while a low shear stress requires a superficial layer that is easy to deform plastically.

    Fortunately, there are several possible routes for materials to get around the contradictory demands. All such possibilities share a common fundament; during tribological contact the material has to transform in such a way that the shear resistance of its outermost layer becomes reduced relative to the hardness of the underlying material.

    This may be achieved in several ways and can involve all sorts of material transformations; phase transformations, deformation hardening, diffusion, smoothening, melting, crystallisation, crystalline rotation, etc. The effect on the friction from these transformations is often very dramatic.

     This presentation will introduce five such working concepts:

    • Surface softening by selective alloy removal and self-ordering
    • Self lubrication on the atomic scale 
    • Deep deformation hardening with superficial softening
    • Smoothening of ultra-hard coating and stabilisation of molecular surface cover
    • Friction melting of thin surface layer

    Illustrating examples be given for each of the concepts, collected from recent research on thin coatings, thick coatings and bulk materials. The mechanisms will be explained, and their potentials demonstrated. Last, a number of outstanding challenges for a widened practical use of these coating concepts will be presented.

  • 49.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Material transfer – an underrated phenomenon in friction2015Conference paper (Refereed)
  • 50.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Resistance to abrasive wear – fundamental and practical aspects: Keynote Lecture2010Conference paper (Refereed)
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