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  • 1.
    Coffin, Douglas W
    et al.
    Miami university, USA.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioekonomi. BiMaC Innovation, Sweden.
    Creasing and folding2017Ingår i: 16th Fundamental research symposium, 2017, s. 69-136Konferensbidrag (Refereegranskat)
  • 2.
    Gimåker, Magnus
    et al.
    RISE., Innventia.
    Nygårds, Mikael
    RISE., Innventia.
    Wågberg, Lars
    Östlund, Sören
    Shear strength development between couched paper sheets during drying2011Ingår i: / [ed] Hirn, U., 2011, , s. 3Konferensbidrag (Refereegranskat)
  • 3.
    Gustafsson, Jan-Erik
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi. RISE., Innventia.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi. RISE., Innventia.
    Loading and deformation of cigarette packages2017Ingår i: 28th IAPRI Symposium on Packaging 2017: Proceedings / [ed] Martine E, 2017, s. 409-Konferensbidrag (Övrigt vetenskapligt)
    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, Bioekonomi. BiMaC Innovation, Sweden.
    Stiffness heterogeneity of multiply paperboard examined with VFM2017Ingår i: 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, s. 151-159Konferensbidrag (Refereegranskat)
    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 strength2016Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 1, s. 123-134Artikel i tidskrift (Refereegranskat)
    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 (2017-2019), Bioekonomi. RISE., Innventia.
    Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation2017Ingår i: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 57, nr 2, s. 325-339Artikel i tidskrift (Refereegranskat)
    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.

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  • 7.
    Hagman, Anton
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi. BiMaC Innovation, Sweden.
    Timmermann, Brita
    Holmen-Iggesund, Sweden.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioekonomi. 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 forming2017Ingår i: 16th Fundamental research symposium, 2017, s. 3-26Konferensbidrag (Refereegranskat)
  • 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 thermography2012Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 2, s. 329-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermography has been used to quantitatively analyze the plastic and elastic energy during deformation of paper. Sack paper samples were subjected to uniaxial tensile testing until rupture occurred. The temperature of the sample was simultaneously recorded with an infrared camera. The mechanical energy invested in the deformation was determined based on the force and deformation data. The thermal energy that accumulated in the sample during testing was estimated using the temperature measurements. Here, special attention was put on using the correct emittance values for the sack paper by measuring it with a new method. When comparing exerted mechanical energy with released thermal energy up to the time of sample rupture, about 40% to 60% of the mechanical energy could be detected as thermal energy. The lacking share of heat was most likely lost due to cooling of the sample during the experiments, as a lower share of detected mechanical energy was obtained for longer experiments. When comparing the increase in thermal energy during rupture to the elastic energy stored in the sample, an agreement of better than 90% was found.

  • 9.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Östlund, Sören
    KTH Royal Institute of Technology, Sweden.
    Nygårds, Mikael
    KTH Royal Institute of Technology, Sweden; BillerudKorsnäs, Sweden.
    Torsional and compression loading of paperboard packages: Experimental and FE analysis2023Ingår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 36, nr 1, s. 31-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present study investigates torsional and compressive loading of a paperboard package. Finite element (FE) analyses simulating the tests were performed to improve understanding of the stresses and deformations in the paperboard during loading. A simple experimental characterization of the necessary material properties could be performed to represent the multi-ply paperboard as a single-ply structure. The results from the single-ply model were compared with a laminate model, and the differences between the models were small. Comparing experimental and FE simulations of box compression and torsion showed that the FE models could accurately predict the response curves. However, in the simulations, there was an overprediction of the maximum compressive force and maximum torque, which was expected since geometrical imperfections and the heterogeneous internal structure of the material were not accounted for in the material model or the FE model. Local yield lines formed at the onset of non-linearities in the package load–displacement curves. Therefore, the strength of the paperboard affects the maximum compressive strength and maximum torque, and the bending stiffness of the paperboard only had a minor effect. When a first local maximum was reached, the number of FE that reached the failure stress increased exponentially. The simulations also showed that box compression was not an effect of package height, but higher packages had a lower maximum torque. © 2022 The Authors. 

  • 10.
    Marin, Gustav
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar. RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Box compression strength of packages in different climates2019Ingår i: 29th IAPRI Symposium on packaging, 2019: Serving society innovative perspectives on packaging, 2019Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 11.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Nygårds, Mikael
    BillerudKorsnäs, Sweden.
    Östlund, S.
    KTH Royal Institute of Technology, Sweden.
    Experimental quantification of differences in damage due to in-plane tensile test and bending of paperboard2022Ingår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 35, s. 69-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Creasing is an essential process to convert paperboards into packages since it enables folding along well-defined lines. The creasing process relies on purpose-made damage that is initiated in the paperboard structure: delamination. However, creasing might also cause in-plane cracks, which must be avoided. In this laboratory study, three paperboards were creased at six different depths, respectively. Two mechanical tests were performed to characterize the creases at standard climate (23°C and 50% RH): 2-point folding, to examine the bending force and short-span in-plane tensile test to evaluate the strength. The results were normalized with the values for the uncreased boards, which gave the relative strength ratios: relative creasing strength (RCS) and relative tensile strength (RTS). When the relative strengths were evaluated against the normative shear strains, a creasing window was formed. This window has an upper limit given by the RTS values, corresponding to the in-plane cracks, and a lower limit given by the RCS values, corresponding to the delamination damage initiated in the paperboard during creasing. It was observed that both the RCS and RTS values exhibit a linear relation against normative shear strain. From this, it was concluded that performing tests at two creasing depths might be sufficient to estimate the lower, and upper, limits for the creasing window in future studies. Finally, the effect of moisture was investigated by creasing, folding and tensile testing at 23°C and 90% RH, which showed that moisture had no clear effect on the RCS or the RTS values. 

  • 12.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Nygårds, Mikael
    RISE Research Institutes of Sweden.
    Östlund, S.
    KTH Royal Institute of Technology, Sweden.
    Stiffness and strength properties of five paperboards and their moisture dependency2020Ingår i: TAPPI Journal, ISSN 0734-1415, Vol. 19, nr 2, s. 71-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Five commercial multiply folding boxboards made on the same paperboard machine have been analyzed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. The paperboards are normally used to make packages, and because the bending stiffness and grammage varies, the performance of the packages will differ. Finite element simulations can be used to predict these differences, but for this to occur, the stiffness and strength properties need to be determined. For efficient determination of the three-dimensional properties in the machine direction (MD), cross direction (CD), and Z direction (ZD), it is proposed that the paperboard should be characterized using in-plane tension, ZD-tension, shear strength profiles, and two-point bending. The proposed setups have been used to determine stiffness and strength properties at different relative humidity (20,% 50%, 70%, and 90% RH), and the mechanical properties have been evaluated as a function of moisture ratio. There was a linear relation between mechanical properties and moisture ratio for each paperboard. When the data was normalized with respect to the standard climate (50% RH) and plotted as a function of moisture ratio, it was shown that the normalized mechanical properties for all paperboards coincided along one single line and could therefore be expressed as a linear function of moisture ratio and two constants. Consequently, it is possible to obtain the mechanical properties of a paperboard by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate (50% RH and 23°C).

  • 13.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Nygårds, Mikael
    RISE Research Institutes of Sweden.
    Östlund, Sören
    KTH Royal Institute of Technology, Sweden.
    Elastic-plastic model for the mechanical properties of paperboard as a function of moisture2020Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 35, nr 3, s. 353-361Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To verify a linear relation between normalized mechanical property and moisture ratio, in-plane tensile tests were performed on four types of paperboard from different manufacturers. Tensile properties were normalized with respect to the property at standard climate (50 % RH, 23 °C). Short-span Compression Tests were also performed to investigate if the relation was linear also for in-plane compression. The tests were performed at different relative humidity (20, 50, 70 and 90 % RH) but with constant temperature (23 °C) in MD and CD, respectively. The linear relation was confirmed for the normalized mechanical properties investigated. In fact, when also the moisture ratio was normalized with the standard climate, all paperboards coincided along the same line. Therefore, each mechanical property could be expressed as a linear function of moisture ratio and two parameters. Moreover, an in-plane bilinear elastic-plastic material model was suggested, based on four parameters: Strength, stiffness, yield strength and hardening modulus, where all parameters could be expressed as linear functions of moisture ratio. The model could predict the elastic-plastic behavior for any moisture content from the two parameters in the linear relations and the mechanical properties at standard climate.

  • 14.
    Marin, Gustav
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar. RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Östlund, Sören
    KTH Royal Institute of Sweden, Sweden.
    Stiffness and strength properties of five paperboards and their moisture dependency2019Ingår i: International Paper Physics Conference 2019, Indianapolis, IN, USA, 5-8 May 2019: preprint proceedings, TAPPI Press, 2019, s. 14-29Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Research has been undertaken to characterise the in-plane and out-of-plane stiffness and strength properties of paperboards to enable data for use in determining constitutive parameters needed in finite element simulations. Paperboards with different bending stiffness were analysed, using five folding box boards of varying grammage (235, 255, 270, 315 and 340gsm). The stiffness and strength properties were determined at different relative humidity (RH), namely, 20, 50, 70 and 90%. As well as in-plane tensile test and out-of-plane tensile test, the short-span compression test (SCT) was carried out, together with bending stiffness test and double-notch shear test. The results revealed a linear relation between mechanical properties and moisture ratio for each paperboard. When the data were normalised with data for the standard climate (50% RH) and investigated as a function of moisture ratio, it was determined that the normalised mechanical properties for all paperboards coincided along one single line. Thus they could be expressed as a linear function of moisture ratio and two constants. It has been concluded that by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate, the mechanical properties of a paperboard could be obtained.

  • 15.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Srinivasa, Prashanth
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Massa, papper och förpackningar.
    Nygårds, Mikael
    BillerudKorsnäs, Sweden.
    Östlund, Sören
    KTH Royal Institute of Technology, Sweden.
    Experimental and finite element simulated box compression tests on paperboard packages at different moisture levels2021Ingår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 34, nr 4, s. 229-243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finite element (FE) analyses can be used as a powerful tool in the package design process to study for instance stress and strain fields that arise during loading. An orthotropic linear elastic material model with a stress-based failure criterion was used to simulate box compression tests (BCTs) of a paperboard package in the FE solver LS-Dyna. Physical experiments were performed at 50%, 70%, and 90% relative humidity (RH). The input parameters required for the simulations were calculated based on material characterization at standard climate (50% RH and 23°C) and a linear relation between mechanical material properties and moisture ratio established in earlier studies. The result showed that it was possible to accurately predict the load–compression curve of a BCT when moisture was accounted for. Furthermore, it was found that modelling of the mechanical properties of the creases are important for capturing the stiffness response of the package. To conclude, it was possible to predict the box compression strength and the linear stiffness response prior to the peak in the load–compression response at relevant moisture levels, by using the previously established linear relationship between moisture ratio and material properties. In addition to the moisture ratio at the preferred moisture level, the only material properties required were the in-plane strengths and stiffnesses, and the out-of-plane shear moduli at standard climate. 

  • 16.
    Nygårds, Mikael
    RISE., STFI-Packforsk.
    Experimental techniques for characterization of elasticplastic material properties in paperboard2008Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 4, s. 432-437Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Nygårds, Mikael
    RISE., STFI-Packforsk.
    Modelling the out-of-plane behaviour of paperboard2009Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 1, s. 72-76Artikel i tidskrift (Refereegranskat)
    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.

  • 18. Nygårds, Mikael
    et al.
    Just, M.
    Tryding, J.
    Experimental and numerical studies of creasing of paperboard2009Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 46, nr 11-12, s. 2493-2505Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    Nygårds, Mikael
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Sjökvist, Stefan
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Marin, Gustav
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Sundström, Jonas
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Simulation and experimental verification of a drop test and compression test of a gable top package2019Ingår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 32, nr 7, s. 325-333Artikel i tidskrift (Refereegranskat)
    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.

  • 20.
    Nygårds, Mikael
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Sjökvist, Stefan
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Marin, Gustav
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Sundström, Jonas
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi, Papperstillverkning och förpackningar.
    Simulation and experimental verification of a drop test and compression test of a Gable top package2019Ingår i: 29th IAPRI Symposium on packaging, 2019: Serving society innovative perspectives on packaging, 2019Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 21.
    Nygårds, Mikael
    et al.
    RISE., Innventia.
    Sundström, Jonas
    RISE., Innventia.
    A comparison between in-plane compression and bending properties2015Ingår i: International Paper Physics Conference, Tokyo, 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 22.
    Nygårds, Mikael
    et al.
    RISE., Innventia.
    Sundström, Jonas
    RISE., Innventia.
    Comparison and analysis of in-plane compression and bending failure in paperboard2016Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 3, s. 432-440Artikel i tidskrift (Refereegranskat)
    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.

  • 23.
    Srinivasa, Prashanth
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi, Papperstillverkning och förpackningar.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioekonomi, Papperstillverkning och förpackningar.
    Hagman, Anton
    RISE - Research Institutes of Sweden, Bioekonomi, Papperstillverkning och förpackningar.
    Pendergraph, Samuel
    RISE - Research Institutes of Sweden.
    Sundström, Jonas
    RISE - Research Institutes of Sweden, Bioekonomi, Papperstillverkning och förpackningar.
    On the torsion method for measurement of out-of-plane shear properties2019Ingår i: International Paper Physics Conference 2019: preprint proceedings, TAPPI Press, 2019, s. 8-13Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Torsional loading with combined out-of-plane compressive loading has been studied for its viability in measurement of out-of-plane shear properties. Paperboards of two qualities were evaluated, namely paperboard A, which was a multiply, while paperboard B was a single ply. Both paperboards were produced on commercial paperboard machines. A total of 24 samples were prepared, 12 of each quality, which were tested under four different load levels. Three different out-of-plane compressive load levels were tested in addition to test without compressive load. Results have been presented from the successful tests in terms of torque versus angle of torsion and shear stress versus shear strain plots. It has been demonstrated that the technique was suitable for out-of-plane shear measurements. An order of magnitude agreement in the values of the properties was obtained in the torsional test method and the rigid block shear tests. Results indicated a possible stable post-peak response in shear loading at sample sizes that would provide material properties comparable with that of a homogeneous test. The torsional setup offered benefit of ease of applying out-of-plane axial loads, both in compression and tension.

  • 24.
    Tryding, Johan
    et al.
    Lund University, Sweden; Tetra Pak, Sweden.
    Marin, Gustav
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioekonomi. RISE., Innventia.
    Mäkelä, Petri
    BillerudKorsnäs, Sweden.
    Ferrari, Guilio
    Tetra Pak, Italy.
    Experimental and theoretical analysis of in-plane cohesive testing of paperboard2017Ingår i: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, Vol. 26, nr 6, s. 895-918Artikel i tidskrift (Refereegranskat)
    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.

  • 25.
    Upadhyaya, Manu
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi.
    Nygårds, Mikael
    RISE - Research Institutes of Sweden, Bioekonomi.
    A finite element model to simulate brim forming of paperboard2017Ingår i: 28th IAPRI Symposium on packaging, 2017, s. 395-408Konferensbidrag (Övrigt vetenskapligt)
1 - 25 av 25
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