| 1. |
- Björk, Elisabeth, et al.
(författare)
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Stock Preparation as a Key Operation for Making High-Quality Wet Moulded Fibre Products
- 2022
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Ingår i: TAPPICon Conference 2022. - : TAPPI Press.
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Konferensbidrag (refereegranskat)abstract
- In the global pursuit for sustainable packaging solutions, usage of different paper raw material is one of the key components to fulfil the goal. Moulded fibre products allow usage of different fibre raw material, although for today, with some restrictions. For example, recycled fibre is of varying quality and can be a challenging material to use for thermoformed wet moulding applications. Further, CTMP strength potential should be further utilized for this application. In both cases, the stock preparation is crucial. The relationship between fibre type, stock preparation, processing and performance needs to be investigated to define how to best produce high-quality wet moulded fibre products using a specific fibre type. To be able to study this a laboratory equipment for manufacturing of high-quality wet moulded fibre products has been set up. Moreover, two test methods to evaluate properties important for trays have been developed; one to evaluate how much load the tray can take and one to evaluate how much the tray will warp during handling. Together with an optimised stock preparation for different fibre raw materials studies can be performed, which aim at increased usage of fibre qualities such as recycled fibre or CTMP for high-quality moulded fibre products.
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| 2. |
- Forsberg, Anton, et al.
(författare)
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PET imaging of amyloid deposition in patients with mild cognitive impairment
- 2008
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Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 29:10, s. 1456-1465
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Tidskriftsartikel (refereegranskat)abstract
- It is of great clinical value to identify subjects at a high risk of developing AD. We previously found that the amyloid positron emission tomography (PET) tracer PIB showed a robust difference in retention in the brain between AD patients and healthy controls (HC). Twenty-one patients diagnosed with MCI (mean age 63.3 ± 7.8 (S.D.) years) underwent PET studies with 11C-PIB, and 18F-fluoro-deoxy-glucose (FDG) to measure cerebral glucose metabolism, as well as assessment of cognitive function and CSF sampling. Reference group data from 27 AD patients and 6 healthy controls, respectively, were used for comparison. The mean cortical PIB retention for the MCI patients was intermediate compared to HC and AD. Seven MCI patients that later at clinical follow-up converted to AD (8.1 ± 6.0 (S.D.) months) showed significant higher PIB retention compared to non-converting MCI patients and HC, respectively (ps < 0.01). The PIB retention in MCI converters was comparable to AD patients (p > 0.01). Correlations were observed in the MCI patients between PIB retention and CSF Aβ1-42, total Tau and episodic memory, respectively.
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| 3. |
- Hagman, Anton
(författare)
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Evaluation of moulded pulp trays using compression test and novel twist test
- 2019
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Ingår i: 29th IAPRI Symposium on packaging, 2019.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Within the industry there exists great experience of producing moulded pulp trays,this includes adjusting process parameters to achieve a consistent output from thetray making machines. However, the evaluation of the results is at this point based onhands on methods that ultimately relies on subjective opinions of what makes a goodtray. This includes visual inspection of the trays, as well as a twisting the trays by handto evaluate stiffness. Such methods might suffice to achieve a consistent output, butare not suited for structured development work, which requires objective measures.One obvious measurement is a compression test, like a box compression test. However, this test does not tell the whole story, and differs from the hands-on tests usedtoday. Because of this a twist test was developed to emulate the hands-on testingpresently used to assess the quality of moulded pulp trays. The test is performed in atensile tester, by putting the tray in a sample holder which supports two diagonal bottom corners while a beam is pressing against the opposite upper diagonal corners.This forces the tray to bend.Plotting the results from these two tests against each other, results in a practicalgraph that can be used to evaluate both pulp and process properties, as well as trayweights. This plot reveals that some information remains hidden if only compressiontests are performed.Finally, such a graph lends itself to define boundaries for what is an acceptable tray.
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| 4. |
- Hagman, Anton, et al.
(författare)
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Experimental and numerical verification of 3D-forming
- 2017
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Ingår i: ADVANCES INPULP AND PAPERRESEARCH,OXFORD 2017. - 9780992616335 ; , s. 3-26
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Konferensbidrag (refereegranskat)abstract
- Motivated by sustainability arguments there is a recent interest informing of advanced structures in paper and paperboard. Therefore,in this paper, hydro-forming of papers and the effect of different fibreraw materials, beating, strength additives (PVAm), grammage andwet and dry papers have been investigated experimentally andnumerically.The experiments were carried out in laboratory hydro-formingdevice. Softwood sheets performed better than hardwood sheets,since they had higher strain at break. The ability of paper to withstandhydro-forming successfully was primarily dependent of the strain atbreak of the paper in relation to the straining required to fill the mould.Forming of wet sheets were also investigated; overall the wet sheetsformed better than the dry sheets, which was due to higher strain atbreak and lower elastic energy. Since the forming was displacementcontrolled, there was no significant difference in the effects of beating,amount of PVAm or grammage.Finite element modelling was performed to identify local strainsand predict problematic regions. Simulations were also performed todetermine how anisotropic sheets would behave, as well as to comparethe process of hydro-forming with press-forming. The papers couldbe strained to higher strain levels than the measured strain at breakbecause the paper is supported by the membrane and mould duringthe forming operation. The maximum strain a paper can withstandcan be increased if the paper can slide into the mould, i.e. by havinga lower coefficient of friction between the steel mould and thepaperboard.During hydro-forming the paper is supported by a rubber membrane,which gives lower strain levels than the corresponding press-formingoperation due to the difference in how the paper is deformed. Pressformingtherefore required paper with higher strain at break. Higherfriction results in more paper being pulled into the mould, whichcontributes to wrinkling of the paper. Simulation of tray forming of acreased sample was performed, which showed that high friction orcompliant creases decreased the circumferential compression.
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| 5. |
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| 6. |
- Hagman, Anton, 1984-
(författare)
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Influence of inhomogeneities on the tensile and compressive mechanical properties of paperboard
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The in-plane properties of paperboard have always been of interest to paper scientists. Tensile properties are crucial when the board is fed through converting machines at high speeds. Compressive properties are essential in the later use. Inhomogeneities affect both the compressive and tensile properties. For the tensile properties, it is the inherent heterogeneity of the paperboard that might cause problems for the board-maker. Varying material properties, through the thickness of the paperboard, are on the other hand used to achieve high bending stiffness with low fiber usage. It is of interest to know how this practice affects the local compressive properties. Papers A and B aims to address this, while C, D and E focus on in-plane heterogeneities. Paper A investigates the mechanism that causes failure in the short span compression test (SCT). It was concluded that the main mechanism for failure in SCT is delamination due to shear damage. In paper B the effect of the through-thickness profiles on the local compression strength was examined. It was concluded that the local compression is governed by in-plane stiffness and through thickness delamination. The latter was in turn dependent on the local shear strength and in-plane stiffness gradients. In paper C the tensile test is investigated with focus on sample size and strain distributions. The strain behavior was dependent on the length to width ratio of the sample and was caused by activation of local zones with high strainability. Paper D focuses on the strain zones seen in C. The thermal response in paper was studied. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. It was concluded that the heat patterns observed coincided with the deformation patterns. It could be shown that the formation was the cause of the inhomogeneous deformation. In final paper, E, the virtual field method was applied on data from C.
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| 7. |
- Hagman, Anton, et al.
(författare)
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Investigation of sample-size effects on in-plane tensile testing of paperboard
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 295-304
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Tidskriftsartikel (refereegranskat)abstract
- The impact of sample size on in-plane strain behavior in paperboard was investigated, with the aim to explore the differences between local and global properties in paperboard, and try to pinpoint the mechanisms behind such differences. The local properties are of interest in converting as well as for future 3D forming of paperboard. It is important to identify differences in behavior between local and global properties since most paperboards are evaluated against the latter. The methods used for evaluation were tensile tests in controlled environment and speckle photography. The results show that there is a difference in strain behavior that is dependent of the length to width ratio of the sample, that this behavior cannot be predicted by standard tensile tests and that it depends on the board composition. The speckle analysis revealed that the behavior is a result of the activation of strain zones in the sample. These zones are relatively constant in size and therefore contribute differently to total strain in samples of different size.
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| 8. |
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| 9. |
- Hagman, Anton, et al.
(författare)
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Investigation of shear induced failure during SCT loading of paperboards
- 2013
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 28:3, s. 415-429
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Tidskriftsartikel (refereegranskat)abstract
- In-plane compression has been analyzed experimentally and numerically using three machine made multiply paperboards. The paperboards had different shear strength profiles. Both short span compression (SCT) and long span compression (LCT) were performed. A finite element model of the SCT setup was developed, and the experimental results in MD and CD could be well predicted by the model. Using the model we could identify that the SCT failure was initiated by shearing of the interfaces in combination with the onset of plasticity in the loading direction. The model was used to make a parameter study. It showed that increased SCT values can be achieved by increasing the stiffness of the board or increase the failure displacement. The increase of stiffness was associated with ply properties, while the failure displacement was associated with interface properties.
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| 10. |
- Hagman, Anton, 1984-
(författare)
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Investigations of In-Plane Properties of Paperboard
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In-plane properties of paperboard have always been of interest to paper mechanical researchers. The reason for this is that they play a large role for the usability of the paperboard throughout its lifespan. Tensile properties are crucial when the board is fed through printing and converting machines at high speeds in the beginning of its life. While compressive properties are essential in the later use of e.g. packages. In this thesis some methods for evaluating in-plane properties are reinvestigated.In Paper A the tensile test was investigated with focus on sample size and strain distributions. Three different multiply paperboards were examined with varying sample sizes using speckle photography. Different strain behaviour was found for different sample sizes. This difference was dependent on the length to width ratio of the sample and was caused by the activation of strain zones in the sample. These zones were of a constant size and therefore occupied different amounts of the total sample area.Paper B investigates the mechanism that causes failure in the short span compression test (SCT). Three different multiply paperboards were examined, this time chosen to have distinctly different through-thickness profiles. The boards were characterized and the data was used to simulate a SCT test with the three different boards. The simulation was conducted with a finite element model consisting of layers of continuum elements with cohesive interfaces in-between. From the model it was concluded that the main mechanism for failure in SCT is delamination that was caused by shear damage.
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