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  • 1.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013). Department of Physics, Faculty of ScienceAssiut University Assiut Egyp.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013), Science, Mathematics and Engineering Education Research.
    Holleboom, Thijs Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Atomistic insights on the wear/friction behavior of nanocrystalline ferrite during nanoscratching as revealed by molecular dynamics2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 3, p. 101-Article in journal (Refereed)
    Abstract [en]

    Using embedded atom method potential, extensive large-scale molecular dynamics (MD) simulations of nanoindentation/nanoscratching of nanocrystalline (nc) iron have been carried out to explore grain size dependence of wear response. MD results show no clear dependence of the frictional and normal forces on the grain size, and the single-crystal (sc) iron has higher frictional and normal force compared to nc-samples. For all samples, the dislocation- mediated mechanism is the primary cause of plastic deformation in both nanoindentation/nanoscratch. However, secondary cooperative mechanisms are varied significantly according to grain size. Pileup formation was observed in the front of and sideways of the tool, and they exhibit strong dependence on grain orientation rather than grain size. Tip size has significant impact on nanoscratch characteristics; both frictional and normal forces monotonically increase as tip radii increase, while the friction coefficient value drops by about 38%. Additionally, the increase in scratch depth leads to an increase in frictional and normal forces as well as friction coefficient. To elucidate the relevance of indentation/scratch results with mechanical properties, uniaxial tensile test was performed for nc-samples, and the result indicates the existence of both the regular and inverse Hall-Petch relations at critical grain size of 110.9 angstrom. The present results suggest that indentation/scratch hardness has no apparent correlation with the mechanical properties of the substrate, whereas the plastic deformation has.

  • 2.
    Gåård, Anders
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Galling resistance of cold work tool materials in sliding against carbon steel2007In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 26, no 1, p. 67-72Article in journal (Refereed)
  • 3.
    Gåård, Anders
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Wear mechanisms in galling: cold work tool materials sliding against high-strength carbon steel sheets2009In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 33, no 1, p. 45-53Article in journal (Other academic)
    Abstract [en]

    Transfer and accumulation of adhered sheet material, generally referred to as galling, is the major cause for tool failure in sheet metal forming. In this study, the galling resistances of several tool steels were evaluated against dual-phase high-strength carbon steel using a SOFS tribometer, in which disc-shaped tools were slid against a real sheet surface in dry sliding test conditions. Three different frictional regimes were identified and characterized during sliding, and any transition in friction corresponded to a transition in wear mechanisms of the sheets. The performance of the tools depended on load, material and the particular frictional regime. Best overall performance was obtained by nitrogen-alloyed powder metallurgy tool steel.

  • 4.
    Gåård, Anders
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science.
    Galling resistance and wear mechanisms - cold work tool materials sliding against carbon steel sheets2007In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 26, no 1, p. 67-72Article in journal (Refereed)
  • 5.
    Gåård, Anders
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Sarih, Rahim M.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Influence of Tool Material and Surface Roughness on Galling Resistance in Sliding Against Austenitic Stainless Steel2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 46, no 2, p. 179-185Article in journal (Refereed)
    Abstract [en]

    Transfer and accumulation of adhered sheet material, generally referred to as galling, is a major cause for tool failure in sheet metal forming. In the present work, the galling resistance of three different tool materials was evaluated in lubricated sliding against austenitic stainless steel using a SOFS tribometer. All tool materials were prepared to four different surface roughnesses, ranging from a polished surface with R (a) = 0.05 mu m to a ground surface with R (a) = 0.3 mu m. The overall best performance was obtained for polished nitrogen alloyed powder metallurgy (PM) tool steel, where galling was detected only at the highest load evaluated, 700 N. However, for both the D2 type tool steel and nodular iron, best performance was observed for the surface possessing a surface roughness of 0.1 mu m. The improved galling resistance for the rougher surfaces was related to filling of grinding scratches with sheet material during the initial stage of sliding, prolonging the development of protruding sheet material on the tools surface. Similar trend was not observed for the PM steel, which was related to width of the scratches originating from the surface preparation, in relation to tool microstructure.

  • 6.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    On the abrasion of ultrafine WC-Co hardmetals by small SiC abrasive2008In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 30, no 1, p. 35-39Article in journal (Refereed)
1 - 6 of 6
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