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  • 1.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, Per-Lennart
    Östlund, Sören
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Karathanasis, Michael
    On material characterization of paper coating materials by microindentation testing2005In: JCT: Journal of Coatings Technology, ISSN 0361-8773, Vol. 2, no 6, p. 463-471Article in journal (Refereed)
    Abstract [en]

    Microindentation as a method for determining important material properties of paper coating materials is studied experimentally and numerically. The bulk of the investigation is concentrated upon the short-lived elastic part of a spherical indentation test, but determination of the failure stress of the coating is also discussed. The results indicate that microindentation can be a powerful tool for material characterization of these materials, but only if careful efforts are made to account for the influence from plasticity as well as from boundary effects

  • 2. Girlanda, Orlando
    et al.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Östlund, S.
    Tryding, J.
    Defect sensitivity and strength of paperboard in the out-of-plane tension and shear2005In: Journal of Pulp and Paper Science, 31(2), 100-104 (2005)Article in journal (Refereed)
  • 3.
    Gåård, Anders
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Krakhmalev, Pavel
    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.
    Temperature effects on adhesive wear in dry sliding contacts2010In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 268, no 7-8, p. 968-975Article in journal (Refereed)
  • 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.
    Hallbäck, Nils
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Girlanda, Orlando
    Tryding, J
    Finite element Analysis of Ink-Tack Delamination of Paperboard2006In: International Journal of Solids and Structures, 43(5), 899–912 (2006)Article in journal (Refereed)
  • 6.
    Hallbäck, Nils
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Korin, Christer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Barbier, Christophe
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Nygårds, Mikael
    KTH.
    Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board2014In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 27, no 9, p. 701-712Article in journal (Refereed)
  • 7.
    Hallbäck, Nils
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Korin, Christer
    Karlstad University, Faculty of Technology and Science, Paper Surface Centre.
    Vähä-Nissi, Mika
    Seppänen, Rauni
    Laine, Christiane
    Influence of paperboard on bond formation and strength of adhesive joint2009Conference paper (Refereed)
    Abstract

    Knowledge about the glueability of fiber-based materials is limited. Factors affecting the adhesive joint between adhesive and paperboard are presented here through two cases: strength of hot melt adhesive joint and consolidation of dispersion adhesive. The hot melt joint was investigated by Y-peel testing, while shear testing was applied for dispersion adhesives. A set of supplementing tools was used to understand the adhesive joints, their development and failure. The results show, for example, the importance of paperboard roughness on the hot melt joint strength. Formation of an adhesive joint with dispersion adhesives is affected by the rheological properties of the adhesive layer and the structure and absorbation properties of the board surface. Both case studies indicate that it can actually be better to apply the adhesive first on a rough surface and the press the smooth surface on the adhesive, which is in contrast with the common practice today

  • 8.
    Hallbäck, Nils
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Tofique, Muhammad Waqas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Development of a distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half-plane2014In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, p. 2878-2892Article in journal (Refereed)
    Abstract [en]

    A distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half plane has been developed. The dipole density distribution is represented with a weighted Jacobi polynomial expansion where the weight function captures the asymptotic behaviour at each end of the crack. To allow for opening and sliding at crack kinking and branching the dipole density representation contains conditional extra terms which fulfil the asymptotic behaviour at each endpoint. Several test cases involving straight, kinked and branched cracks have been analysed, and the results suggest that the accuracy of the method is within 1% provided that Jacobi polynomial expansions up to at least the sixth order are used. Adopting even higher order Jacobi polynomials yields improved accuracy. The method is compared to a simplified procedure suggested in the literature where stress singularities associated with corners at kinking or branching are neglected in the representation for the dipole density distribution. The comparison suggests that both procedures work, but that the current procedure is superior, in as much as the same accuracy is reached using substantially lower order polynomial expansions.

  • 9.
    Hämäläinen, Pyry
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Hallbäck, Nils
    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).
    Lestelius, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    On the determination of transverse shear properties of paper using the short span compression test2017In: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 107, p. 22-30Article in journal (Refereed)
    Abstract [en]

    The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko-Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young's modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko-Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose.

  • 10.
    Korin, Christer
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Barbier, Christophe
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nygårds, Mikael
    KTH Royal Institute of Technology, Solid Mechanics.
    Finite Element Analysis of Hot Melt Adhesive Joints in Carton BoardManuscript (preprint) (Other (popular science, discussion, etc.))
  • 11.
    Korin, Christer
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Junghans, R
    Failure Modes of Adhesively Joined Carton Board2008In: Journal of Adhesion Science and Technology, 2008Article in journal (Refereed)
  • 12.
    Korin, Christer
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Junghans, Robert
    Failure Modes of Adhesive Joints in Carton Board2008In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 22, p. 2079-2104Article in journal (Refereed)
  • 13.
    Korin, Christer
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre.
    Lestelius, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science.
    Tryding, J
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Y-peel Characterization of Adhessively-bonded Carton Board an objective Method2007In: Journal of Adhesion Science and Technology 21 2007 (2) 197-210Article in journal (Refereed)
  • 14.
    Korin, Christer
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Seppänen, Rauni
    YKI, Institute for Surface Chemistry.
    Vähä-Nissi, Miki
    VTT Technical Research Centre of Finland.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Influence of surface treatments on the mechanical strength of hotmelt adhesive joints made of cartonboards2012In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 26, no 20-21, p. 2339-2356Article in journal (Refereed)
    Abstract [en]

    The influence of surface treatments including pigment coating, surface sizing and calendering on the mechanical strength of hotmelt adhesive joints in pilot made cartonboards was studied. The mechanical strength of the joints was investigated using the Y-peel test device at 23 degrees C and 50% relative humidity. Some of the samples were investigated with respect to the failure mode by scanning electron microscopy. The surfaces were characterized in terms of surface roughness, surface chemical composition, and adhesion behaviour. A strong adhesive bond displayed fibre tear. In addition to fibre tear, interfacial failure, i.e., failure between the cartonboard and the adhesive, was the main reason for fracture in the bonded assembly. The most important factor controlling the integrity of adhesive joints seemed to be the real contact area. The adhesive joints showed significantly higher strength when the hotmelt adhesive was first applied onto the rougher cartonboard of the assembly and then the smoother cartonboard was pressed on the adhesive than vice versa. The surface roughness of cartonboards mainly depended on whether the surface was pigment coated or not. Calendering displayed only a minor effect. No clear influence of surface chemical composition of the cartonboards on the adhesive joint strength was found due to the fact that changes in surface chemistry in this study also led to changes in surface roughness. The strongest adhesive joint was created between two medium-rough and surface-sized cartonboards.

  • 15. Nygårds, M
    et al.
    Just, M.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Tryding, J.
    A finite Element Model for simulations of Creasing and Folding of PaperBoard2005Conference paper (Refereed)
  • 16.
    Sadek, Mohamed
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hallbäck, Nils
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Burman, Christer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    20 kHz 3-point bending fatigue of automotive steels2018In: MATEC Web of Conferences, EDP Sciences, 2018, Vol. 165, p. 1-7, article id 22020Conference paper (Refereed)
    Abstract [en]

    The 20 kHz load frequency enables fatigue tests for very high cycle fatigue life, 109-1013 cycles, within conveniently short time. In automotive applications, many components are subjected to flexural loading and hence bending fatigue is an important test mode. Ultrasound fatigue test instruments have been used successfully in several assessments of fatigue strength and more commonly in uniaxial loading. Here, a 3-point bending fatigue test rig operating in resonance at 20 kHz load frequency has been designed to test plane specimens at R=0.1 loading. The test rig design and stress calculations are presented. Testing for fatigue strength was conducted using the staircase method with 15 specimens of each steel grade, specimens reaching 108 cycles were considered run-outs giving fatigue strength at 108 cycles. Additional 15 specimens of each grade were tested for S-N curves with the upper limit above 109 cycles. Two different common automotive steels, 38MnSiV5, a micro-alloyed ferritic-pearlitic steel, and 16MnCr5, a carburizing martensitic steel, were tested. The fatigue strengths achieved from the staircase testing are 340 and 419 MPa stress amplitudes for the 38MnSiV5 and 16MnCr5 steels, respectively. The S-N curves of the steels appear to be quite flat in the tested life range 107 - 109.

  • 17.
    Tofique, Muhammad Waqas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Burman, Christer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science.
    Gåård, Anders
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fatigue strength, crack initiation, and localized plastic fatigue damage in VHCF of duplex stainless steels2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 7, p. 899-910Article in journal (Refereed)
    Abstract [en]

    The fatigue strength of two-duplex stainless steel grades, 2304 SRG and LDX 2101, with austenitic–ferritic microstructure is tested using ultrasonic fatigue testing equipment operating at 20 kHz. The testing is conducted in tension-compression mode with the load ratio R=-1. The fatigue strength is evaluated at 107, 108, and 109 load cycles and the estimates of fatigue strength are higher for the LDX 2101 grade. The fatigue crack initiation mechanisms are analyzed using a scanning electron microscope. The fatigue cracks, in all cases, appear to initiate due to accumulation of plastic fatigue damage at the surface. In the 2304 SRG grade, accumulation of fatigue damage occurs at the external surface of fatigued specimens in the form of extrusions at the grain/phase boundaries and in the form of individual slip lines in the austenite phase. Meanwhile, in the LDX 2101 grade accumulation of plastic fatigue damage in the form of extrusions and intrusions occurs mainly within the ferrite grain. When the crack is microstructurally short, the crack growth appears to be crystallographic in nature and the crack appears to change its direction propagating from one grain into another.

  • 18.
    Tofique, Muhammad Waqas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Hallbäck, Nils
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Burman, Christer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Fatigue initiation and strength of duplex stainless steel strip specimens in the very high cycle fatigue regime2014In: Very high cycle fatigue 6 (VHCF6), 2014Conference paper (Refereed)
    Abstract [en]

    Fatigue studies of cold-rolled duplex stainless strip steel were performed in the very high cycle fatigue life region. The duplex austenitic-ferritic microstructure gives this grade a combination of high mechanical strength and high corrosion resistance. Fatigue properties of thin steel strips are particular due to cold rolling introducing a very fine microstructure. Crack initiation and fatigue strength are controlled by steel microstructure and alloying. The initiation and growth of the very short initial fatigue crack in very high cycle fatigue are unclear and subject to different descriptions. Fatigue test data of thin strip specimens at very high fatigue lives are scarce due to testing difficulties. For practical reasons testing must be performed at ultrasound test frequencies which involves fixturing problems. A test setup including the load chain ultrasonic horn, fixture and specimen was designed for resonance with a horse-shoe design of a screw fixture. The design of the horse-shoe fixture and the specimens along with FEM calculation of eigenfrequency are presented. Fatigue testing was performed at 20 kHz in R=-1 conditions up to fatigue life of 107 to 5*109 cycles. Fatigue strength was tested and crack initiation was studied on the fracture surface using FEG-SEM at the initiation site.

  • 19.
    Tofique, Muhammad Waqas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Development of the distributed dislocation dipole technique for the analysis of closure of complex fractures involving kinks and branches2018In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 69, p. 168-178Article in journal (Refereed)
    Abstract [en]

    This paper presents the development of the distributed dislocation dipole technique (DDDT) for the analysis of straight, kinked and branched cracks where parts of the cracks may close during loading. The method has been developed for plane problems. Crack cases in which closure occurs are analyzed by reformulating the Buecicner's principle, taking into account the contact stresses at the contacting portions of the crack surfaces. Stress intensity factors corresponding to opening and the in-plane sliding mode of deformation at the crack tips are computed. Several test cases involving straight, kinked and/or branched cracks where parts of the cracks undergoes crack surface closure when subjected to the outer loading are analyzed. The results obtained from the DDDT are compared to those obtained from a Finite Element Method (FEM) analysis of the same crack cases. This comparison shows that the computation of stress intensity factors for the cases involving crack surface closure are less accurate than those for fully open crack cases. However, for the cases under consideration, the stress intensity factors were still computed with a maximum difference of approximately 2 per cent compared to the FEM calculations if Jacobi polynomial expansions of at least the twelfth order were used to represent the crack surface opening and sliding displacements. In most cases under consideration, sixth order Jacobi polynomial expansions were sufficient to obtain results within that margin of deviation.

  • 20.
    Tofique, Muhammad Waqas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Hallbäck, Nils
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Development of the distributed dislocation dipole technique for the analysis of closure of complex fractures involving kinks and branchesManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents the development of the distributed dislocation dipole technique (DDDT) for the analysis of crack surface closure of crack cases involving kinks and branches. Crack cases in which closure occurs are analyzed by reformulating the Bueckner's principle taking the contact stresses at the contacting portions of the crack surfaces into account. Stress intensity factors corresponding to opening and sliding mode of deformation at the crack tips are computed. Three test cases involving kinked and/or branched cracks with at least one of the crack segments undergoing crack surface closure when subjected to remote tensile loading are analyzed. The results obtained from the DDDT are compared to those obtained from the Finite Element Method (FEM) analysis of the same crack cases. This comparison shows that the computation of stress intensity factors for the crack cases involving crack surface closure are less acurate compared to fully open crack cases. However, the stress intensity factors are still computed to an accuracy of within 2 percent if the Jacobi polynomial expansions of at least the sixth order are used to represent the crack surface opening and sliding displacements. Higher order Jacobi polynomials lead to increased accuracy.

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