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  • 1.
    Abu Baker Karim, Aria
    et al.
    Örebro University, School of Science and Technology.
    Schnelzer, Anna
    Örebro University, School of Science and Technology.
    Optimering av glidlager och utveckling av dess konstruktion2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We have in this project become engrossed in a plain bearing design that is located in a screw press. The screw press compact an unknown mass that is confidential. Robustus have a suggestion to over dimensioning the present plain bearing. The aim of this project was to analyze and to do an optimization on some plain bearings and compare them to the present bearing and to take the choice of material and the environment where the bearing is located into account. The analysis and the optimizations showed that the current plain bearing had the best geometry but not the optimal material selection. The project is in an early state and it needs some geometrical changes. The most important of everything is that the problem has been identified with the help of the wrecked plain bearing and with an excel model.

  • 2.
    Gåård, Anders
    et al.
    Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Karlstads universitet, Karlstad, Sweden.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Krakhmalev, Pavel
    Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Karlstads universitet, Karlstad, Sweden.
    Broitman, Esteban
    Tunnfilmsfysik, Linköpings universitet, Linköping, Sweden.
    Nano-scale friction of multi-phase powder metallurgy tool steels2015In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1119, p. 70-74Article in journal (Refereed)
    Abstract [en]

    Friction is a fundamental phenomenon in tribology involving complex mechanisms between thecontacting surfaces. Measurements of friction are often made using devices with substantially largercontact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials,influence of particular microstructural constituents is not resolved. In the present work, a tribometerwith a contact area in the nano-scale range was used to map friction for different types of tool steelswith different chemical- and phase composition. Owing to the small tip radius, frictionalcharacteristics of primary carbides and the steel matrix were measured and compared. Dependingon chemical composition, a difference was observed where the coefficient of friction wasapproximately twice higher for the steel possessing highest coefficient of friction, including bothcarbides and the steel matrix.

  • 3.
    Karlsson, Patrik
    Karlstad university, Karlstad, Sweden.
    The influence of tool steel microstructure on galling2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a sort of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, the overall aim was to gain knowledge of the influence of tool steel microstructure on galling initiation under sliding conditions. It was discovered that material transfer and tool steel damage caused by sheet material flow creating wear-induced galling initiation sites occurred in the early stage of galling. The galling resistance was higher for tool steels with higher matrix hardness due to better resistance to tool steel damage. Initial friction and critical contact pressure to galling was influenced by the strength of the sheet material. Material transfer happened at low pressures and the friction value was high in a case of sheet materials with lower proof strength, possibly due to the sheet contact against the tool steel matrix resulting in high adhesion and quicker tool damage. It was demonstrated that, in addition to hardness of the tool steel matrix and sheet material proof strength, tool steel microstructural features like size, shape, distribution and height of hard phases are important parameters influencing galling. Tool steels comprising homogeneously distributed, small and high hard phases better prevented the contact between sheet material and the tool steel matrix. Thus, a metal to metal contact with high friction was more efficiently avoided, which resulted in better tool performance.

     

  • 4.
    Karlsson, Patrik
    et al.
    Karlstad University, Karlstad, Sweden.
    Eriksson, Jenny
    Dalarna University, Falun, Sweden.
    Gåård, Anders
    Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Karlstad University, Karlstad, Sweden.
    Olsson, Mikael
    Dalarna University, Falun, Sweden.
    Bergström, Jens
    Karlstad University, Karlstad, Sweden.
    Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming2012In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 24, no 6, p. 263-272Article in journal (Refereed)
    Abstract [en]

    Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65 HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright © 2012 John Wiley & Sons, Ltd.

  • 5.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of tool steel microstructure on friction and initial material transfer2014In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 319, no 1-2, p. 12-18Article in journal (Refereed)
    Abstract [en]

    An investigation was conducted to study the influence of tool steel microstructure on initial material transfer and friction. Two different powder metallurgy tool steels and an ingot cast tool material were tested in dry sliding against 1.4301, 1.4162, Domex 355 MC and Domex 700 MC sheet materials. It was found that tool steel hard phase heights influence initial material transfer and friction. The coefficient of friction increased with decreasing tool steel hard phase heights at 50 N normal load and initial material transfer occurred around protruding hard phases. At higher load of 500 N the sheet material adhered to both the tool steel matrix and hard phases. Coefficient of friction decreased with increasing proof strength of the sheet material at 500 N normal load.

  • 6.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Galling Resistance and Wear Mechanisms for Cold Work Tool Steels in Lubricated Sliding Against High Strength Stainless Steel Sheets2010In: Tribology of manufacturing processes: Proceedings of the 4th International Conference on Tribology in Manufacturing Processes (ICTMP 2010), Volume 2 / [ed] Eric Felder; Pierre Montmitonnet, Paris: Presses de l'Ecole des mines , 2010, p. 673-682Conference paper (Refereed)
  • 7.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Galling resistance and wear mechanisms for cold-work tool steels in lubricated sliding against high strength stainless steel sheets2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 286-287, p. 92-97Article in journal (Refereed)
    Abstract [en]

    Tool damage in sheet metal forming of stainless steel is of high concern for the forming industry. In the present work, ingot cast AISI D2 and advanced powder metallurgy tool steel (PM) cold-work tool steels were evaluated and ranked regarding wear mechanisms and galling resistance. Wear tests were performed using a slider-on-flat-surface (SOFS) tribometer in sliding against austenitic–ferritic (duplex) stainless steel sheets at different contact pressures in lubricated conditions. The best galling resistance was observed for the nitrogen alloyed PM tool steels. Abrasive scratching of the tool surfaces and transfer of sheet material due to adhesive wear were the main metal forming tool surface damage mechanisms. By increasing the hardness of one PM sheet metal forming tool grade, the galling resistance was enhanced.

  • 8.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of size and distribution of hard phases in tool steels on the early stage of galling2012In: TOOL 2012: proceedings of the 9th international tooling conference, developing the world of tooling, Montanuniversität Leoben 11-14 September 2012 / [ed] Herald Leitner, Regina Kranz, Angelika Tremmel, Knittelfeld: Verlag "Gutenberghaus" , 2012Conference paper (Refereed)
    Abstract [en]

    In sheet metal forming processes, contact pressures are relatively high and total sliding distances are long, which demands tool steels to prevent tool damage and to resist galling. Galling is related to microscopic and macroscopic material transfer, but, the mechanisms of initiation are not thoroughly understood.

    To investigate galling initiation, lubricated sliding testing in the Slider-On-Flat-Surface (SOFS) tribometer was performed for ingot cast (IC) AISI D2 type and nitrogen alloyed powder metallurgy (PM) tool steel. The sheet grade was EN 1.4509 ferritic stainless steel. To reveal mechanisms in the early stages of galling initiation, transfer and accumulation of sheet material to the tool surfaces were characterized using AFM and SEM.

    It was found that already after a short sliding distance, transfer of sheet material occurred covering both the matrix and the hard phases. Macroscopic analysis of the contact area showed that initial material transfer and further lump growth occurred at positions corresponding to high plastic strains in the sheet material. Even though initial material transfer was observed for both tested tool steels, the sliding distance to the point where transfer and further lump formation occurred was longer for the PM tool steel. This was discussed in correlation to differences in size and distribution of the hard phases in the tool steels, which was confirmed by AFM and SEM.

  • 9.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Berhe-Larsson, Johanna
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of tool steel hard phase orientation and shape on galling2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 966-96, p. 249-258Article in journal (Refereed)
    Abstract [en]

    Conventionally manufactured cold work tool steel is often used in sheet metal forming as die material. Due to the forging process, the as-cast network structure of carbides is broken into elongated particles. Depending on the tool cross-section, the orientation and shape of carbides in the active tool surface is different. In the present research, the influence of tool steel hard phase orientation and shape on galling was investigated. D2 type tool steel was cut in three different orientations and tested in lubricated sliding conditions against AISI 304 austenitic stainless steel. Tests were performed using a Slider-On-Flat-Surface and galling was detected by changes in friction and post-test microscopy. The lubricant was Castrol FST8 using 5 g/m2 sheet material. Results showed a strong correlation between sliding distance to galling and tool steel hard phase orientation and shape at low loads, whereas high load contact resulted in early galling in all cases. Material transfer was observed mainly to the tool steel matrix. The worst performance was observed for specimens cut so that the tool steel hard phase, M7C3 carbides in the D2 steel, were oriented along the sliding direction, which resulted in longer open tool matrix areas contacting the sheet material.

  • 10.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Bergström, Jens
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of work material proof stress and tool steel microstructure on galling initiation and critical contact pressure2013In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, p. 104-110Article in journal (Refereed)
    Abstract [en]

    EN 1.4301 (austenitic), EN 1.4509 (ferritic), EN 1.4162 (duplex) and EN 1.4310 C1000 (metastable austenitic) stainless steels were tested in lubricated sliding against an ingot cast EN X153WCrMoV12 and powder metallurgy nitrogen alloyed Uddeholm Vancron 40 tool steels to reveal critical to galling contact pressure, Pcr. The calculated Pcr were higher for steels with higher strength. At P>Pcr, due to plastic flow of sheet material, the tool is damaged substantially and wear-induced matrix damage causes rapid galling initiation. At P<Pcr, galling was not observed. The powder metallurgy tool steel was more resistant to galling against all tested stainless steels. Better performance was associated with fine and homogeneously distributed hard phases preventing intensive wear of the tool steel matrix.

  • 11.
    Larsson, Joakim
    et al.
    Örebro University, School of Science and Technology.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    The effect of bearing length on the surface quality of drawn wire2019Conference paper (Refereed)
    Abstract [en]

    In wire drawing, the geometry of drawing dies influences the performance of the wire process. This study investigates the effect of bearing lengths on the surface quality of the drawn wire. Wire drawing tests were done using an industrial wiredrawing machine utilizing drawing dies with different bearing lengths. The influence of bearing length on surface quality is discussed.

1 - 11 of 11
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