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  • 1.
    Coffin, Douglas W
    et al.
    Miami university, USA.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Creasing and folding2017In: 16th Fundamental research symposium, 2017, p. 69-136Conference paper (Refereed)
  • 2.
    Gimåker, Magnus
    et al.
    RISE, Innventia.
    Nygårds, Mikael
    RISE, Innventia.
    Wågberg, Lars
    Östlund, Sören
    Shear strength development between couched paper sheets during drying2011In: / [ed] Hirn, U., 2011, , p. 3Conference paper (Refereed)
  • 3.
    Gustafsson, Jan-Erik
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Loading and deformation of cigarette packages2017In: 28th IAPRI Symposium on Packaging 2017: Proceedings / [ed] Martine E, 2017, p. 409-Conference paper (Other academic)
    Abstract [en]

    Research has been undertaken to investigate the deformation properties of cigarette packages subjected to different loads. Numerical simulation enables a hypothetical package produced from a hypothetical paperboard to be tested. A finite element model was implemented in the Abaqus system in order to calculate stresses and strains in the deformed packages. The model behaves as expected up to deformations with limited damage. The calculated initial slopes of the reaction force responses were generally in good agreement with the corresponding measured slopes, although the model had a nonlinear force response that was not found in the experimental data. Incorporating cohesive behaviour into the model would allow the elements to disconnect from each other. Statistical analysis of the couplings between the initial process responses and the material properties of the paperboards revealed that only the initial yield stress parameter significantly affected the slope.

  • 4.
    Hagman, Anton
    et al.
    KTH Royal Institute of Technology, Sweden; BiMaC Innovation, Sweden.
    Considine, J M
    USDA Forest Service, USA.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Stiffness heterogeneity of multiply paperboard examined with VFM2017In: Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems. Conference Proceedings of the Society for Experimental Mechanics Series (CPSEMS) vol. 9, 2017, 2017, Vol. 9, p. 151-159Conference paper (Refereed)
    Abstract [en]

    Mechanical heterogeneity of a multiply paperboard was characterized in uniaxial tension using DIC and VFM. The specimen was divided into three subregions based on axial strain magnitude. VFM analysis showed that the subregions had stiffnesses and Poisson’s ratio’s that varied in a monotonically decreasing fashion, but with the stiffness differences between subregions increasing with applied tensile stress. An Equilibrium Gap analysis showed improved local equilibrium when comparing a homogeneous analysis with the subregion analysis. Although only a single specimen was examined, results suggest that high stiffness regions provide only marginal improvement of mechanical behavior. The analysis also showed that even though the subregions themselves were non-contiguous, their mechanical behavior was similar.

  • 5.
    Hagman, Anton
    et al.
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Nygårds, Mikael
    RISE, Innventia.
    Short compression testing of multi-ply paperboard, influence from shear strength2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 1, p. 123-134Article in journal (Refereed)
    Abstract [en]

    The influence of the through-thickness shear strength profiles on the short span compression test was examined. This was done both with experiments and finite element simulations on five industrial produced paperboards. It was concluded that the short span compression test is governed by in-plane stiffness and through thickness delamination. The delamination damage was in turn dependent on the local transverse shear strength and in-plane stiffness gradients. Furthermore, it was concluded that the pre-delamination mechanisms were elastic. Finally it was possible to alter the results from the test by altering the shear strength of the paperboard; this should be done uniformly over the entire middle ply of the board if an increased SCT value was what was sought after.

  • 6.
    Hagman, Anton
    et al.
    KTH Royal Institute of Technology, Sweden.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation2017In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 57, no 2, p. 325-339Article in journal (Refereed)
    Abstract [en]

    The thermal response in paper has been studied by thermography. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Because of its fibrous network structure, paper has an inhomogeneous micro-structure, which is called formation. It could be shown that the formation was the cause of the inhomogeneous deformations in paper. Finite element simulations was used to show how papers with different degrees of heterogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid compaction of the paper was created during the creping process. During tensile testing this was recovered as the paper network structure was strained.

  • 7.
    Hagman, Anton
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Timmermann, Brita
    Holmen-Iggesund, Sweden.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. BiMaC Innovation, Sweden.
    Lundin, Andreas
    Barbier, Christophe
    Billerud-Korsnäs, Sweden.
    Fredlund, Mats
    Stora Enso, Sweden.
    Östlund, Sören
    KTH Royal Institute or Technology, Sweden.
    Experimental and numerical verification of 3D forming2017In: 16th Fundamental research symposium, 2017, p. 3-26Conference paper (Refereed)
  • 8.
    Hyll, Kari
    et al.
    RISE, Innventia.
    Vomhoff, Hannes
    RISE, Innventia.
    Nygårds, Mikael
    RISE, Innventia.
    Analysis of the plastic and elastic energy during the deformation and rupture of a paper sample using thermography2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, no 2, p. 329-334Article in journal (Refereed)
  • 9.
    Marin, Gustav
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Box compression strength of packages in different climates2019In: 29th IAPRI Symposium on packaging, 2019: Serving society innovative perspectives on packaging, 2019Conference paper (Other academic)
    Abstract [en]

    Packages made of five folding box boards made on the same paperboard machinehave been analysed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. Thepaperboards are normally used to make packages, and since the bending stiffnessand grammage varies the packages performance will be different. In this study, twodifferent load cases were defined and Box Compression Tests (BCT) were performedat different levels of relative humidity (30, 50, 70, 90 % RH) and were evaluated as afunction of moisture ratio.The result showed a linear relation between the box compression strength and themoisture ratio. In addition, when the data was normalized with the measurements forthe standard climate (50 % RH) and was evaluated as a function of moisture ratio, theresult indicated that the normalized box compression strength for all the paperboardsand both of the load cases could be expressed as a linear function of moisture, dependent of two constants a and b.Consequently, the study indicates that it is possible to estimate the Box compressionstrength at different climates of a package made of paperboard, by knowing the boxcompression strength for the standard climate (50 % RH and 23 °C) and the constantsa and b.

  • 10.
    Nygårds, Mikael
    RISE, STFI-Packforsk.
    Experimental techniques for characterization of elasticplastic material properties in paperboard2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 4, p. 432-437Article in journal (Refereed)
    Abstract [en]

    Four experimental techniques to characterize elastic-plastic material properties for paperboard are presented. To evaluate properties as a function of paperboard thickness the bottom, middle and top plies were separated by grinding. The different plies have been characterized with respect to in-plane tension, cyclic ZD tension, out-of-plane shear and cyclic ZD compression. These tests were chosen since they are easily interpreted in term of stresses and strains, and give a good set of elastic-plastic material properties that are needed to describe the mechanical properties of the materials. For the ZD tension and compression tests several loading/unloading cycles were used in order to evaluate how the elastic modulus evolves as a function of deformation. For the ZD tension it was observed that the elastic modulus degrade faster than the strength. For all tests functions that describe the stress-strain curves are proposed and hence material parameters with a physical interpretation were introduced.

  • 11.
    Nygårds, Mikael
    RISE, STFI-Packforsk.
    Modelling the out-of-plane behaviour of paperboard2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 1, p. 72-76Article in journal (Refereed)
    Abstract [en]

    A material model consisting of a continuum and an interface model was proposed. When the models are used together the mechanical properties of paperboard can be accounted for. The continuum model was elastic-plastic in shear and compression, while only elastic in tension. In the continuum model two different yield surfaces were used to initiate plastic deformation; one for compression and one for combined shear and normal stresses. The elastic-plastic interface model accounts for separation in the normal and tangential directions. The models have been numerically implemented into the finite element software Abaqus (2007). The implementations were used to show that the response of a cyclic tension and cyclic compression test can be predicted. Moreover, simulations with combined compression and shear stresses were presented.

  • 12. Nygårds, Mikael
    et al.
    Just, M.
    Tryding, J.
    Experimental and numerical studies of creasing of paperboard2009In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 46, no 11-12, p. 2493-2505Article in journal (Refereed)
    Abstract [en]

    A laboratory creasing device to capture the most important properties of a commercial rotary creasing tool was designed. Finite element analysis of the creasing of a multiply paperboard in the laboratory crease device was presented. The multiply paperboard was modeled as a multilayered structure with cohesive softening interface model connecting the paperboard plies. The paperboard plies were modeled by an anisotropic elastic-plastic material model. The purpose of the analysis of the laboratory creasing device was to present material models that represent paperboard, and to investigate how well the analysis captured the multiply paperboard behavior during laboratory creasing. And to increase the understanding of what multiply paperboard properties that influence the laboratory crease operation. The result of the simulations showed very good correlations with the experimental obtained results. The results indicated that the paperboard properties that have the most influence is the out-of-plane shear, out-of-plane compression and the friction between the laboratory creasing device and the paperboard. © 2009 Elsevier Ltd. All rights reserved.

  • 13.
    Nygårds, Mikael
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Sjökvist, Stefan
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Marin, Gustav
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Sundström, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Simulation and experimental verification of a drop test and compression test of a gable top package2019In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 32, no 7, p. 325-333Article in journal (Refereed)
    Abstract [en]

    A finite element framework has been proposed that can be used to simulate both empty paperboard packages and package filled with plastic granulates. A gable top package was made of a commercial paperboard, and material properties needed in the material model were determined. Two simulations were performed, a drop test and a compression test. By comparison between experimental and numerical results, the deformation mechanisms at impact could be identified and correlated to material properties. When the package was filled with granulates, different mechanisms was activated compared with an empty package. The granulates contribute to bulging of the panels, such that the edges became more load bearing compared with the panels. When the edges carried the loads, the importance of the out-of-plane properties also increased, and local failure initiation related to delamination was observed. Comparison between experimental and numerical impact forces shows that there are still important things to consider in the model generation, eg, variation of properties within the package, which originate both from material property variations, and the loading history, eg, during manufacturing and handling.

  • 14.
    Nygårds, Mikael
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Sjökvist, Stefan
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Marin, Gustav
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Sundström, Jonas
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Simulation and experimental verification of a drop test and compression test of a Gable top package2019In: 29th IAPRI Symposium on packaging, 2019: Serving society innovative perspectives on packaging, 2019Conference paper (Other academic)
    Abstract [en]

     A finite element framework has been proposed that can be used to simulateboth empty paperboard packages and package filled with plastic granulates. A Gabletop package was made of a commercial paperboard, and material properties neededin the material model was determined. Two simulations were performed, a drop testand a compression test. By comparison between experimental and numerical results,the deformation mechanisms at impact could be identified and correlated to materialproperties. When the package was filled with granulates different mechanisms wasactivated compared to an empty package. The granulates contribute to bulging ofthe panels, such that the edges became more load bearing compared to the panels.When the edges carried the loads the importance of the out-of-plane properties alsoincreased, and local failure initiation related to delamination was observed. Comparison between experimental and numerical impact forces show that there are still important things to consider in the model generation, e.g. variation of properties withinthe package, which originate both from material property variations and the loadinghistory, e.g. during manufacturing and handling.

  • 15.
    Nygårds, Mikael
    et al.
    RISE, Innventia.
    Sundström, Jonas
    RISE, Innventia.
    A comparison between in-plane compression and bending properties2015In: International Paper Physics Conference, Tokyo, 2015, 2015Conference paper (Other academic)
    Abstract [en]

    For paperboard that have a ZD gradient, the in-plane compression and bending properties were correlated. At peak load the paperboard delaminated.A Timoshenko beam analysis showed that when the bottom ply failed, delamination would be initiated.For three paperboards that were different in character, good prediction of failure load and delamination position could be made by only consider the tensile strength profiles and the shear strength profiles.

  • 16.
    Nygårds, Mikael
    et al.
    RISE, Innventia.
    Sundström, Jonas
    RISE, Innventia.
    Comparison and analysis of in-plane compression and bending failure in paperboard2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 3, p. 432-440Article in journal (Refereed)
    Abstract [en]

    In-plane compression of paperboard, using long (LCT) and short compression test (SCT), and bend-ing, using the L&W creasability tester, have been ana-lyzed using three paperboards with similar strength prop-erties but different ZD profiles. The failure loads from the methods have been compared and the failure mechanisms analyzed. It was shown that at maximum bending moment from bending of samples using L=10 mm and L=50 mm, the SCT value and the maximum bending force from LCT all varied linearly with each other, indicating that same dam-age mechanism is activated. It was suggested that delamination cracks were initiated during SCT and LCT as well as during bending when plastic deformation had been initiated in an outer ply subjected to compressive stress. The plastic deformation would be initiated when the yield stress in the ply was reached, determined by an in-plane tensile test. When plastic deformation takes place, it will generate shear induced delamination cracks in locations with low shear strengths, e.g. in the interfaces or within the middle ply. The location depends on the material design strategy used in manufacturing the paper quality. To control the in-plane compression properties in pa-perboard one should control the yield stress (or possibly the failure stress) of the outer plies. Increased stress gives higher in-plane compression strength. Moreover, the interfaces strength is important, since increased interface strength (or lack of interfaces) prevents delamination.

  • 17.
    Tryding, Johan
    et al.
    Lund University, Sweden; Tetra Pak, Sweden.
    Marin, Gustav
    RISE - Research Institutes of Sweden, Bioeconomy.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Mäkelä, Petri
    BillerudKorsnäs, Sweden.
    Ferrari, Guilio
    Tetra Pak, Italy.
    Experimental and theoretical analysis of in-plane cohesive testing of paperboard2017In: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, Vol. 26, no 6, p. 895-918Article in journal (Refereed)
    Abstract [en]

    In-plane cohesive failure of paperboard was characterized by short-span uniaxial tension tests. Six paperboards’ qualities were experimentally investigated, from which cohesive stress-widening curves were extracted. A fracture energy was defined, expressed in the tensile strength and maximum slope of the cohesive stress-widening relation. Analytical cohesive relations were derived based on the tensile strength and maximum slope, utilizing the Morse potential for diatomic molecules. It was experimentally found that the maximum slope and fracture energy depend on the tensile strength. The ratio of the maximum slope to the elastic modulus (stable length) was shown to be independent of the tensile strength.

  • 18.
    Upadhyaya, Manu
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy.
    A finite element model to simulate brim forming of paperboard2017In: 28th IAPRI Symposium on packaging, 2017, p. 395-408Conference paper (Other academic)
1 - 18 of 18
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