Dissertations / Theses on the topic 'Paperboard'
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Hauptmann, Marek, Andre Schult, Roland Zelm, Tilo Gailat, Alexander Lenske, Jens-Peter Majschak, and Harald Großmann. "Gastight Paperboard Package." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-126236.
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Packages made from coated paperboard are currently used in food packaging for frosted or microwave food. These cups are usually deep drawn from flat paperboard blanks. The blanks are pre-creased to control the material overflow that appears during drawing. The resulting wrinkles in the sealing area have to be considered as capillary tubes allowing the gas exchange between the package and the environmental atmosphere. A new technological approach in 3D forming enables the prevention of capillary tubes in the sealing area. The result is a gas-tight sealable paperboard cup which is limited by its coating concerning the degree of gas tightness.
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Dunn, Heather M. (Heather Margaret) 1976. "Micromechanisms of paperboard deformation." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/50630.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (p. 245-246).
An experimental study of the micromechanisms of paperboard deformation has been conducted. Experiments were performed in a scanning electron microscope, allowing visual observation and coincident acquisition of load vs. deformation data. Deformation mechanisms were determined and correlated with features of the load vs. deformation curves for different loading modes. A macroscopic study was performed concurrently to provide accurate continuum-level load vs. deformation data. This study contributed to an effort to model the creasing process. In creasing, paperboard is punched to create an internal line of damage and then folded along that line to create a corner. It has been determined experimentally that the creasing process involves through-thickness compression and transverse shear loading, as well as in-plane tension loading. Out-of-plane delamination also plays an important role. Experiments were conducted to determine the stress-strain behavior and corresponding deformation mechanisms under several well-controlled loading conditions. These include through-thickness compression, shear, and tension, as well as combined tension/shear loading. In-plane tensile behavior was also investigated. Paperboard loaded in out-of-plane compression behaved linearly at small strains, with an exponential increase in stiffness at larger strains. Deformation mechanisms included void closure and fiber collapse. In out-of-plane shear, paperboard initially behaved linearly, but departed from linearity before a peak in load. The dominant failure mechanism at the microscopic scale was sudden fiber disengagement throughout the entire cross-section, corresponding to the peak in load. Loaded in out-of-plane tension, the paperboard first exhibited many small cracks at the interfaces between layers. As these cracks grew, one became dominant, and all further delamination occurred by extension of that crack. Similar behavior was observed in combined loading experiments with tension as the larger load component. With shear as the larger component, delamination generally occurred suddenly rather than being preceded by small local cracks. In-plane tensile behavior also included an initial linear region, followed by nonlinearity and a peak in load. The dominant mechanisms were fiber break and fiber disengagement in the different layers of the board; this again corresponded to the ... [missing rest of abstract]
by Heather M. Dunn.
S.M.
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Marin, Gustav. "In-plane fracture of paperboard." Thesis, KTH, Hållfasthetslära (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-178798.
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In order to prevent the occurrence of cracks in paper packages, the in-plane mechanical behavior for the full paperboard needs to be investigated. Further, it is of importance to understand also the in-plane behavior of the plies that build up the paperboard. In order to characterize the crack growth behavior, a normalized stress-widening model was developed, based on the minimum fracture energy, according to Tryding (2014). The model depends on the tensile strength, _t, and the maximum slope after peak stress in short-span tensile tests, Nmax. In this Master's thesis, it was investigated if the normalized stress-widening model is a true master curve, which describes the crack growth in full paperboards, and in their plies, respectively. To verify if the model is a true master curve, six paperboards from three di_erent suppliers were investigated. From short-span tensile tests, the properties needed for the stress-widening model were obtained. The results indicate that the normalized stress-widening model is a true master curve, which also is valid for unloading. Furthermore, a linear relation between _t and Nmax was obtained, which means that the model might be reduced to be dependent of the tensile strength, _t, and a constant that will be de_ned empirically by the linear relation between _t and Nmax. All three-ply boards were based on sandwich construction theory, which was supported by the results, were two paperboards, Paperboard A and Paperboard C had signi_cantly larger tensile strength, in comparison to their density, than Paperboard D and Paperboard E, which indicates that Paperboard A and Paperboard C have better material distribution than Paperboard D and Paperboard E. From the thesis, it can be concluded that, by performing short-span tensile tests, it is possible to normalize the post-peak stress behavior for paperboards into a master curve. Since all paperboards that have been investigated follow the master curve, it can be concluded that the fracture behavior can be characterized by the three parameters that a_ect the model, i.e. the tensile strength, _t, the maximum slope after peak stress, Nmax, and the tensile sti_ness, E.
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Guo, Zhiling. "Torsional Stiffness of Corrugated Paperboard." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1477434308012406.
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Runesson, Lisa. "Numerical and experimental study of embossing of paperboard : A material characterization of one specific paperboard quality." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-44380.
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This master thesis has its main focus within embossing operations and how different factors influence the result. The work was performed at Stora Enso Research Centre in Karlstad, Sweden. Embossing is relatively complex operation to analyze since the paperboard can be exposed of both bending, shear and compression at the same time. The techniques used today for evaluating embossing on paperboard consist of experimental setups. These experimental techniques needed to be complemented in order to simplify the approach for embossing evaluations. The aim of this thesis was to develop a simulation material model, created with Finite Element Method by using Abaqus (2014), which capture the experimental behavior of embossed paperboard. The goals were to understand which material properties that are of high importance in embossing operations, and how sensitive the simulation material model is at small geometry changes of the embossing tool. A three dimensional finite element material model has been created in Abaqus (2014). The analysis was performed as dynamic quasi-static where an implicit solver was used. The simulation material model consisted of a continuum model, which describes the behavior of the plies, and an interface model implemented as cohesive elements, which describes the inelastic delamination between the plies. The continuum model was defined as an anisotropic linear elastic-plastic material model with isotropic linear hardening together with Hill´s yield criterion. The interface model was defined with an anisotropic elastic-plastic traction-separation law and an exponential damage evolution model. The purpose of the experimental tests was to capture the behavior of embossed paperboard and the goal was then to recreate the behavior in the simulation model. The results in this thesis focus on the relationship between the applied force and the displacement. An experimental and numerical study of out-of-plane compression has also been conducted, where the aim was to determine the out-of-plane elastic modulus, EZD. According to embossing results, the embossing results showed an exponential hardening behavior while the numerical results, unfortunately, showed a declining hardening behavior. Despite this, some understanding regarding which parameters that are of utmost importance have been achieved. The material parameters which had the highest influence on embossed paperboards seem to be the out-of-plane shear properties. This thesis also shows that the material model is sensitive of small changes of the tool geometry. The proportion of shear, bending and compression are strongly dependent on if the tool has sharp edges or if the edges are more rounded.
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Weyrauch, Thomas. "The Paperboard Testing-Machine : Development Process." Thesis, KTH, Hållfasthetslära (Inst.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92639.
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The design of a paperboard testing machine, developed in order to analyse the mechanical behaviour of paperboard during the combined of out-of-plane shear and compressive loading as in the deepdrawing process, is presented. The methodology to design a paperboard testing machine is discussed and the most appropriate concepts are compared and evaluated. The design process is presented in detail, and some pilot tests are performed to give an overview about the functionality of the manufactured prototype.
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Zhang, Feng. "Price Behavior of Paper and Paperboard Industry." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7266.
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This paper presents a model of the probability of price response to the previous periods inventory absolute and relative level for U.S. paper and paperboard industry. The initial part of the paper contains a theoretical analysis of the phenomenon. The proposed framework indicates that the inventory level plays an important leading role in the price adjustment.
The model is then estimated with monthly data extending from 1980 to 1999. The LPM and Probit models are used to estimate the effect of absolute and relative inventory level on the probability of price variations. The estimated results are in agreement with the oligopolistic market condition of U.S. paper and paperboard industry, showing the price upward adjustment is sticker and rigid than the price downward adjustment while the output level is indifferent to the previous months inventory fluctuation.
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Annapragada, Sriram Kiran. "Mechanism of Foaming on Polymer-Paperboard Composites." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19790.
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This thesis addresses a new technique of foaming on polymer-paperboard composites which combines the advantages of traditional polymeric foam with the environmental benefits of paperboard. Paperboard is sandwiched between two extruded polymeric layers of different densities. On application of heat, one face is foamed by the evaporating moisture in the board; the other face serves as a barrier. This work is directed at gaining a better understanding of the fundamental processes in foaming polymers on paperboard. The ultimate goal is to be able to produce uniform bubbles of a predetermined size on the surface so as to give optimum heat insulation and good tactile properties. Bubble growth was studied as a function of paperboard properties, polymer melt index, extrusion speed, polymer thickness, temperature and moisture content. The foam quality (thickness) is also related to the cell size distribution and various factors affecting it are identified. A combination of experimental techniques such as high speed imaging, infrared thermography and scanning electron microscopy is used for this purpose. Foaming on paper-polymer composites is caused by water vapor escaping through the pores present in the paperboard substrate and then foaming the polymer. The vapor driving force which dominates foaming and overcomes the less significant viscoelastic and surface tension opposition forces depends on the paperboard properties as well as on the ability of the polymer to bond with the paperboard. It was found that the bubble size distribution directly relates to the pore size distribution on the paperboard. The bubble size was also controlled by the thickness of the polymer layer and its ability to bond with the paperboard. Coalescence subsequently led to thicker foams due to the formation of larger sized bubbles.
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Hagman, Anton. "Investigations of In-Plane Properties of Paperboard." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123158.
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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.QC 20130603
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Wretstam, Sofia. "Characterization of property variations in paperboard samples." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233469.
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In today’s paper and board production, quality control is made on a single cross direction (CD)sample from each tambour. As several different properties are analysed, only a limited number of measurement results are obtained for one property. Therefore, the measurement results might not be representative for the properties of the entire width of the tambour. The first objective of the project was to investigate variations of thickness, surface roughness and mechanical properties with a much higher resolution and number of measurements. The results of the measurement were compared with the routine quality control of the mill. The second objective of the project was to evaluate the influence of the wire shake unit in the centreply on the properties of the produced board. The measurements were performed on Iggesundpaperboard samples.The high-resolution measurements were performed using the STFI structural thicknessmeasurement device, an OptiTopo topography measurement device and a modified Autolinedevice at RISE Bioeconomy. The statistical evaluation of the results was performed in Matlab.Standard deviation, local variance and a frequency analysis were calculated for the thicknessmeasurements. Only standard deviation was considered for the topography data. For the mechanical properties, the distribution was evaluated using the Weibull distribution, since theresults had a single-sided distribution. In addition, the properties were analysed as a function of their location, for example to identify deterministic deviations in cross direction.The results of the first part of the project showed that the everyday control conducted in Iggesund is sufficient for most of the properties. Greatest difference was found at the edges ofthe samples, where Iggesund standard quality control does not detect a major variation inproperties, as no measurements are performed that close to the edge of the web. For example,at one edge, the high frequent measurements showed a significant drop in thickness which were not detected with the everyday quality control.In the second part of the project, the effect of a shake unit on the paper properties was evaluated. Here it was seen that the thickness variation were reduced, which also can be interpreted as an improvement of formation in the centre ply of the paperboard. As for thesurface roughness a slight improvement was found. Also for the mechanical properties, the shake unit appeared to improve the uniformity of the productI dagens pappers-och kartongproduktion görs kvalitetskontroll på en enda tvärremsa (CD) från varje tambour. Eftersom flera olika egenskaper analyseras, erhålls endast ett begränsat antal mätresultat för en egenskap. Därför är informationen begränsad och kanske inte representativ för hela bredden av tambours egenskaper. Projektets första mål var att undersöka variationer i tjocklek, ytjämnhet och mekaniska egenskaper med mycket högre upplösning och antal mätningar. Resultaten av mätningen jämfördes med brukets rutinmässiga kvalitetskontroll.Det andra syftet med projektet var att utvärdera effekten av viraskaken på egenskaperna hos den producerade kartongen. Samtliga mätningar utfördes på kartongprover från IggesundsBruk.Mätningarna med hög upplösning utfördes med hjälp av en STFI-mätare för strukturtjocklek,en OptiTopo-enhet och en modifierad L&W Autoline-enhet. Den statistiska utvärderingen avresultaten utfördes i Matlab. Standardavvikelse, lokal variation och en frekvensanalys beräknades för tjockleksmätningarna. Endast standardavvikelse utvärderades för ytråhetsdata.För de mekaniska egenskaperna utvärderades fördelningen med hjälp av Weibullfördelningen,eftersom resultaten visade ett ensidigt beteende. Dessutom analyserades egenskaperna som en funktion av deras placering, till exempel för att identifiera deterministiska avvikelser i tvärriktningen.Resultaten av projektets första del visade att den dagliga kontrollen i Iggesund är tillräcklig för de flesta egenskaperna. Den största skillnaden hittades vid provets kanter, där Iggesundsstandardkvalitetskontroll Missar stora variationer för vissa egenskaper, eftersom inga mätningar utförs i det området på produkten. Vid ena sidan av nätverket visade de högfrekventa mätningarna en betydande minskning av tjockleken.I den andra delen av projektet utvärderades effekten av en skakningsenhet på pappersegenskaperna. Här såg man att variansen i tjockleksmätningarna indikerar en förbättring av formationen i kartongens mittskikt. När det gäller ytråheten konstaterades en liten förbättring. För de mekaniska egenskaperna föreföll viraskaken förbättra produktenslikformighet.
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Babbepalli, Venkata Venu Sai Phani Ram. "Implementation of moisturedependent constitutive model for paperboard." Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284356.
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There has been a considerable increase in the usage of paper products due to its sustainability in the product cycle. Many environmental and process variables can affect the mechanical behavior of paper from its making to finished products. Of these variables, moisture is of particular importance and strongly influences both papermaking, converting, and end-use of the paper products. Experimental investigations at different humidity levels reveals that normalized in-plane constitutive parameters, such as elastic parameters and the linear hardening modulus, in both MD and CD1) follow a linear relationship with normalized moisture ratio. This relation is found to be acceptable for a wide range of commercial paperboards. To capture this observation, a novel material model with orthotropic elasticity and anisotropic hardening2 is proposed. An associative flow rule for the evolution of plastic strain is proposed. The proposed flow rule is such that all stresses contribute to plastic flow rather than an effective stress. A simple version using anisotropic linear hardening is implemented. The mechanical properties, such as elastic parameters and hardening moduli are considered functions of the moisture ratio. An implicit variant of the material model is implemented in LS-DYNA®. The simulations with the proposed material model at different humidity levels follow the experimental results well for uniaxial loading, but discrepancies are obtained for simulation of biaxial loading tests. The moisture is assumed constant in the proposed model since the experiments are done in a moisture-controlled environment.Användningen av pappersprodukter har ökat avsevärt på grund av dess hållbarhet i produktcykeln. Många miljö- och processvariabler kan påverka papperets egenskaper från tillverkning till färdig produkt. Av dessa variabler är fukt särskilt viktig och fukt påverkar kraftigt både tillverkning, konvertering och slutanvändning av pappersprodukter. En experimentell undersökning vid olika fuktighetsnivåer visar att normaliserade konstitutiva parametrar, såsom elastiska styvheter och tangentmodulen i papperets plan i både MD och CD, uppvisar ett linjärt samband som funktion av normaliserad fuktkvot. Detta samband har visat sig vara en god approximation för ett stort antal kommersiella kartonger. En ny materialmodell baserad på ortotrop elasticitet och anisotropt hårdnande föreslås med hänsyn till detta. En associativ flytlag för plastisk deformation föreslås. Den föreslagna flytlagen är sådan att alla spänningar bidrar till den plastiska deformationen snarare än effektivspänningen. En enklare version baserad på linjärt anisotropt hårdnande har modellerats. De mekaniska egenskaperna såsom styvhet och hårdnandemodul anses vara funktioner av fuktkvoten och följa de linjära sambanden. En implicit variant av materialmodellen är implementerad i LS-DYNA®. Simuleringar med den föreslagna materialmodellen vid olika fuktkvoter följer de experimentella resultaten väl vid enaxlig belastning medan vissa avvikelser uppträder vid tvåaxlig belastning. I den föreslagna modellen antas fukten antas vara konstant eftersom de bakomliggande experimenten genomfördes i en fuktkontrollerad miljö.
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Bi, Wu. "Racking Strength of Paperboard Based Sheathing Materials." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1091059928.
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Sjöstrand, Björn. "Evaluation of Compression Testing and Compression Failure Modes of Paperboard : Video analysis of paperboard during short-span compression and the suitability of short- and long-span compression testing of paperboard." Thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper (from 2013), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-27519.
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The objectives of the thesis were to find the mechanisms that govern compression failures in paperboard and to find the link between manufacturing process and paperboard properties. The thesis also investigates two different test methods and evaluates how suitable they are for paperboard grades. The materials are several commercial board grades and a set of hand-formed dynamic sheets that are made to mimic the construction of commercial paperboard. The method consists of mounting a stereomicroscope on a short-span compression tester and recording the compression failure on video, long-span compression testing and standard properties testing. The observed failure modes of paperboard under compression were classified into four categories depending on the appearance of the failures. Initiation of failure takes place where the structure is weakest and fiber buckling happens after the initiation, which consists of breaking of fiber-fiber bonds or fiber wall delamination. The compression strength is correlated to density and operations and raw materials that increase the density also increases the compression strength. Short-span compression and Long-span compression are not suitable for testing all kinds of papers; the clamps in short-span give bulky specimens an initial geometrical shape that can affect the given value of compression strength. Long-span compression is only suitable for a limited range of papers, one problem with too thin papers are low wavelength buckling.
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Lei, Lei. "Computer Usage and Demand for Paper/Paperboard Products." Thesis, Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-04062007-134445/.
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Tufvesson, Helena. "The mechanisms of edge wicking in retortable paperboard." Licentiate thesis, Stockholm, Division of Fibre Technology, Department of Fibre and Polymer Technology, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4155.
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Huang, Hui. "Numerical and Experimental Investigation on Paperboard Converting Processes." Doctoral thesis, KTH, Hållfasthetslära (Avd.), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-125883.
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An investigation of the mechanical properties of paperboard and its influence on converting processessuch as creasing, folding and forming, from both an experimental and numerical perspective wasperformed. Fundamental research to establish a material model for paperboard, and an experimentalout-of-plane shear test method was suggested. Research where the models were used for verificationwas also done. The numerical model is a combination of continuum and interface models. Thecontinuum model represents the paperboard plies, which is an orthotropic elastic-plastic model withHill criteria and isotropic hardening. The interface model is used for connecting the paperboard pliesand also contributing to the delamination properties during converting processes. The interface modelhas linear elastic behavior followed by the initiation and evolution of damage. Both of these twomodels are available in ABAQUS. An experimental characterization scheme consisting of threeexperiments: in-plane tensile test, double notch shear test and density measurements, was shown to besufficient to predict the creasing and folding behavior.The creasing and folding performance can be well predicted by the model. The impact of ply andinterface properties on different paperboards were investigated by numerical simulations, in order tomimic different production strategies. It was shown that the interface strengths mainly influenced thefolding behavior, whereas different ply properties affected the required creasing force.The forming investigation was conducted in a three dimensions deep pear-shape mould. The numericalinvestigation included the effect of pressure, boundary conditions, material properties, differentdeformation and damage mechanisms, i.e. delamination and plasticity. The results showed thesimulation can capture the failure pattern of experiments and the mechanisms during forming. Toachieve better forming performance with anisotropic commercial paperboard in an axis-symmetricmould, a combination of fixed and free boundary conditions can be used to minimize in-plane straincomponents while enabling delamination. Modification of material properties would enable an evenbetter optimization. Additionally, reduction of anisotropy can improve the forming performance.QC 20130815
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Xia, Qingxi 1973. "Mechanics of inelastic deformation and delamination in paperboard." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8334.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 233-236).
Paperboard is one of the most widely used materials. The inelastic deformation of paperboard plays a crucial role during many manufacturing processes (e.g., the converting process whereby paperboard is converted into a product such as a milk carton by punching and subsequent folding) and during in-service applications. There is a scarcity of constitutive models describing inelastic behavior of paperboard under complex loading, despite the paper industry's great need of analytical tools to aid the design and manufacturing of better paperboard products. In this thesis, two constitutive models are developed to model the highly anisotropic, elastic-plastic behavior of paperboard/paper: (1) A three-dimensional elastic-plastic interface constitutive model is developed to model the out-of-plane delamination behavior of paperboard. The onset of interface separation is controlled by a limit surface in the normal-shear traction space. The limit surface is taken to shrink with a monotonically-increasing scalar internal variable reflecting damage associated with the history of inelastic relative interface displacement. (2) A three-dimensional, anisotropic continuum constitutive model is developed to model the in-plane elastic-plastic deformation of paper and paperboard. The proposed initial yield surface is directly constructed from the yield strengths measured in various loading directions and the corresponding ratios of plastic strain components. An associated flow rule is used to model the plastic flow of the material. Anisotropic strain-hardening of yield strengths is introduced to model the evolution of the yield surface with inelastic strain.
(cont.) The two constitutive models are implemented into finite element software to enable the simulation of paperboard mechanical behavior under complex, finite deformation. The models are shown to be capable of accurately capturing both the out-of-plane delamination (via the interface model) and the anisotropic in-plane elastic-plastic (via the continuum in-plane model) behavior of paperboard under complex loading. The two models are combined to simulate the mechanics of a converting process (creasing and subsequent folding) of paperboard. The simulations agree well with corresponding experimental observations. In particular, the underlying mechanisms of damage and delamination development during creasing and subsequent folding are predicted well; the macroscopic response of the bending moment vs. bending angle also agrees with experimental data. This research provides physically based three-dimensional material models of the anisotropic, elastic-plastic deformation of paperboard that enable the computational design of paperboard process and product design.
by Qingxi Steve Xia.
Ph.D.
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Johansson-Näslund, Markus. "Numerical analysis of paperboard delamination using cohesive elements." Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277779.
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A new test method for measuring the shear strength associated with mode III delamination of paperboard is studied with the purpose of reducing the size of the test configuration. The method, which uses a split cantilever beam (SCB) specimen, measures the shear strength indirectly through the fracture resistance. The methodology is based on the double cantilever beam (DCB) specimen, used for measuring the normal delamination strength of paperboard. The study is based on finite element analyses, where cohesive elements are implemented for predicting the fracture response. An experimental evaluation of the test method was carried out in a pre-study conducted between Karlstad, Skövde and Lund University together with Tetra Pak. The experiments considered both the SCB-specimen and the standardised DCB-specimen, and for determination of the fracture behaviour the cohesive law presented by Tryding & Ristinmaa (2017) were considered. The result obtained from the experiments is used as a basis for evaluating the analyses. To model the fracture development, the relation presented by Tryding & Ristinmaa (2017) is implemented in the commercial finite element software Abaqus through a user-specified element. From the analyses of the DCB-specimen it is shown that through implementation of a specified cohesive law, it is possible to simulate mode I fracture development of paperboard in an accurate manner. The results for the DCB analyses correlate well with the experimental results. The result for the SCBspecimen shows a deviating behaviour from the experimental result by underestimating the shear strength. It is noted that the specimen is subjected to notable deformations in both the first shear direction and the normal direction, preventing pure shear loading from being obtained. Based on the analyses, it is indicated that the current test configuration does not obtain pure shear separation in mode III, and thereby underestimates the actual shear strength of the paperboard. It is also shown that reducing the specimen length with 400 mm has no significant impact on the properties related to the cohesive law. By altering the initial crack length, it is possible to further reduce the length of the specimen. However, to prevent development of unstable fracture, the length of the paperboard should exceed 300 mm. Alternating the crack length and the width of the paperboard also seems to contribute to lower displacements in the normal direction and provides a better fit with the experiments. Tryding, J. & Ristinmaa, M. (2017). Normalization of cohesive laws for quasi-brittle materials. Engineering Fracture Mechanics, 178, 333-345. doi:10.1016/j.engfracmech.2017.03.020En ny testmetod för att mäta skjuvstyrkan för modus III delaminering av kartong studeras i syftet att reducera testutrustningens storlek. Testmetoden, som använder sig av en delad konsolbalk (SCB), mäter skjuvstyrkan indirekt genom brottresistansen. Metodiken är baserad på det standardiserad konsolbalks testet DCB, var två balkar är sammankopplade och som används för att mäta delaminering styrkan i kartongens normala riktning. Studien baseras på analyser med finita element, var kohesiva element implementeras för att prediktera brottbeteendet. En experimentell utvärdering av testmetoden genomfördes i en förstudie mellan Karlstads, Skövdes och Lunds universitet tillsammans med Tetra Pak. Experimenten gjordes både för DCB- och SCB-testet, och för att utvärdera brottbeteendet användes de kohesiva lagarna som presenterats av Tryding & Ristinmaa (2017). De experimentella resultaten används som bas vid utvärdering av analyserna. För att modellera spricktillväxten implementeras de kohesiva lagarna i det kommersiella FEM programmet Abaqus genom ett användar specificerat element (UEL). Från analyserna av DCB-testet visas det att det är möjligt att simulera modus I sprickbildning i kartong genom implementering av en specifik kohesive lag. Simuleringarna av DCB-testet stämmer väl överens med de experimentella resultaten. Resultaten från SCB-analyserna visar däremot på ett avvikande beteende från experimenten genom att underskatta skjuvstyrkan. Det noteras i analyserna av SCB-testet att märkbara deformationer i både den första skjuvriktningen och normal riktningen uppkommer, vilket förhindrar att ren skjuvbelastning i modus III erhålls. Baserat på analysernas resultat indikeras det att den nuvarande konfiguration för SCB-testet inte ger ren skjuvbelastning i modus III och underskattar därför kartongens faktiska skjuvstyrka. Det visas också att en 400 mm reducering av SCB-geometrins längd inte har någon märkbar påverkan på de kohesiva egenskaperna. Genom att ändra den initiala spricklängden är det möjligt att ytterligare reducera SCBgeometrins längd. För att försäkra sig om att sprickas tillväxt förblir stabil bör däremot längden på kartongen överstiga 300 mm. Att minska den initiala spricklängden och bredden på kartongen verkar generellt bidra till lägre deformationer i normal riktningen och ett resultat som ligger närmare de experimentella. Tryding, J. & Ristinmaa, M. (2017). Normalization of cohesive laws for quasi-brittle materials. Engineering Fracture Mechanics, 178, 333-345. doi:10.1016/j.engfracmech.2017.03.020
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Liang, Yiming. "Analysis of Paperboard Performance using Digital Image Correlation." Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277799.
Full textAbstract:
The performance of paperboard materials in packaging application has been investigated and evaluated for a long time. This is because it plays a decisive role for product protection and decoration in packaging applications. Potential damages during transportation sometimes affect the consistency of the performance. Therefore, the capability of the material to resist these external disturbances was of interest. A multiply paperboard was chosen as the experimental material. The analysis conducted in this thesis aimed to reveal the tensile behavior in the cross-machine direction (CD) of the material against various kinds of local or global changes. The changes included global and local climate variations, cutouts, and regional weakening and strengthening, which were applied during the intervals between preloading and reloading. The digital image correlation (DIC) analysis computed the time-varying strain fields from the gray level information contained in the recorded videos of loading processes. The generated strain fields were imported to post analysis. Comparison between comparable stages (two stages with the same average strain value from different loading sections) was considered as the scheme of isolating the influences of the changes and investigating them individually. The cosine image similarity method and the eigenface algorithm were used to validate this scheme, while the directional average calculation and the strain field compensation method were introduced to realize the isolation. The differences between the front and back outer plies of the paperboard sheets were detected as individual. Moreover, both global and local climate changes were affecting the strain distributions of the specimens proportionally on account of the moisture ratio within the material. In addition, the invisible mechanical weakening and strengthening were captured evidently with the analysis, which caused strain concentrations due to the uneven distribution of expansion capability. The relaxation and bending in unloading processes were two of the primary disturbing factors within all the deformed specimens, which were related to time and bending direction, correspondingly.Egenskaperna hos kartongmaterial för förpackningstillämpningar har varit ett ämne att undersökning under lång tid. Detta för att dessa egenskaper spelar en avgörande roll som produktskydd och dekorativ utformning i mängde av tillämpningar. Potentiella skador under transport påverkar bland annat materialets tillförlitlighet och prestandard. Därför är det aktuellt att undersöka samt förstå materialets förmåga att motstå yttre störningar. Experimentmaterialet som användes bestod av en typ av flerskiktskartong. Analyser som utfördes i denna avhandling har syfte att identifiera de mekaniska förändringarna i materialets dragegenskaper i tvärsmaskin-riktningen (CD) på grund av olika lokala eller globala förändringar. Förändringarna innefattar både globala och lokala klimatvariationer, utskärningar, och lokala försvagningar samt förstärkningar. Dessa förändringar infördes vid intervallet mellan på- och avlastning. Den digital bildkorrelations analys (DIC) användes för att beräknade de tidsvarierande töjningsfälten från den grånivåinformationen i som registrerades med hjälp av inspelade videor under belastningen Den genererade töjningsfälten importerades för vidare analys. Två tillstånd med liknande medelvärde av töjningsnivån från olika delar av belastningen jämfördes, detta för att isolera påverkan av förändringarna och undersöka dem individuellt. Två olika metoder för jämförelse av bilderna (cosine image similarity och eigenface algorithm) användes för att validera analysschemat, där riktning-medelvärdesberäkningar och töjningsfälts kompensations-metoden användes för att realisera dessa isoleringar. Enstaka skillnader upptäcktes mellan de främre och bakre ytskikten på kartongarken. Dessutom påverkades töjningsfördelningarna för proverna både av den globala och lokala klimatförändringar på grund av fukttillståndet i materialet. Vidare kan de osynliga mekaniska försvagningar och förstärkningar tydligt fångas med de utförda analyserna, vilket ledde till töjningskoncentrationers uppkomst på grund av det inhomogena expansions-förmåga hos arket. Relaxationen och böjningen vid avlastning relaterade till tid och böjningsförmåga var två av de primära faktorerna som påverkade analysens kvalité.
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Smith, Carmen Alexis. "Micromechanics of the through-thickness deformation of paperboard." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9426.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 171-172).
An experimental investigation of the behavior of paperboard has been performed, focusing on the identification of the mechanisms of through-thickness deformation. Experiments have been conducted at the microscopic and macroscopic levels, the difference between the two being the length scale. Experiments at the microscopic level were performed in a scanning electron microscope, allowing concurrent viewing of the deformation as it took place with acquisition of load vs. displacement data. The experiments at the macroscopic level confirm the mechanisms observed at the microscopic level and provide more accurate, continuum-level stress-strain data. The motivation for the investigation is the modeling of the creasing process, in which a sheet of paperboard is punched and folded along a narrow line to create a corner for packaging. Creasing experiments indicate that out-of-plane shear damage during punching and normal delamination during folding govern the quality of the resulting crease. Experiments in out-of-plane tension, compression, and simple shear have been performed to investigate the behavior of paperboard under these simple loading conditions. The results show that normal and tangential delamination at the interfaces between layers is of extreme importance in the behavior of paperboard in tension and shear. Damage in the form of micro cracks occurs almost from the onset of strain and culminates in large-scale delamination coincident with a large decrease in the strength of the material. In compression, the behavior is mostly elastic and is governed by densification of the material. The brief initial stages of deformation involve plastic elimination of voids. This is followed by non-linear elastic stiffening of the material via densification.
by Carmen Alexis Smith.
S.M.
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Huang, Hui. "Numerical and experimental investigation of paperboard creasing and folding." Licentiate thesis, KTH, Hållfasthetslära (Inst.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31430.
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This licentiate thesis aims to increase the understanding of deformation and damage mechanisms of paperboard during converting, especially creasing and folding will be analyzed. A simple two dimensional creasing simulation was performed. In this model, paperboard was modeled as a combination of an anisotropic elastic-plastic continuum model with isotropic hardening and a softening cohesive interface model. The paperboard was composed of four plies with uniform material parameters. Creasing simulations were done on both machine direction (MD) and cross machine direction (CD) samples to two crease depths 0.0 mm and 0.2 mm, respectively. The simulation results showed good agreement with experimental results. The out-of-plane shear properties are dominating factors for creasing and folding. Therefore, a test method to determine shear properties was proposed. This part of the work is based on the most recently proposed test method, the laminated double notch shear test. To improve the technique, double notches with declined slopes, called tilted double notch shear test, were used instead of uniform depth double notches. The influence of shear zone length was also investigated. The results reveal the short shear zone lengths gave higher shear strength and more pronounced shear strength profile. The results from the rst two analyses were utilized to study folding of paperboard. The simulation model was the same as in the creasing simulations. However, to improve the model and better account the actual micro structure of paperboard a new material mapping method was proposed. The continuum properties of the plies were assumed to vary in the thickness direction. The shear strengths of the interfaces were determined by using the tilted double notch shear test using a short shear zone length, L= 5 mm. The agreement between simulation results and experiment results was good, and most of the folding properties were captured.QC 20110317
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Skoglund, Anders. "Multivariate modelling and monitoring for stabilisation of paperboard manufacturing /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek903s.pdf.
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Wallmeier, Malte, Marek Hauptmann, and Jens-Peter Majschak. "The Occurrence of Rupture in Deep-Drawing of Paperboard." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-215931.
Full textAbstract:
The production of paperboard packaging components in fast-running machines requires reliability of the production process. Boundaries for the process parameters and constraints for the geometry of the tools require investigation to determine dependable configurations. This paper aimed to investigate the relationships between process parameters, tool geometry, and the occurrence of rupture in the deep-drawing process of paperboard. Different types of ruptures in various phases of the process were distinguished and linked to their specific cause. An extensive experimental investigation with multiple variables of influence was conducted. A logistic regression model was used to describe the experimental data and was statistically validated. The blankholder force was found to be the most influential parameter. Interactions between the parameters blankholder force, punch velocity, and punch diameter were recognized. A high punch velocity can reduce the probability of rupture when the punch diameter is adjusted.
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Marin, Gustav. "On the relation between paperboard properties and packaging performance." Licentiate thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287377.
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Paper-based materials, such as paperboard, are commonly used as packaging materials. Inaddition to the advantage that wood as a raw material is renewable, there are also many otherbenefits of paperboard. From a mechanical point of view, paperboard has a high bendingstiffness compared to its relatively low weight and has a high foldability, which both areproperties of significance in the design of packages. However, a distinct drawback withpaperboard is its significant sensitivity to moisture. The moisture reduces the mechanicalproperties of the paperboard and consequently reduces the performance of the package. Thisthesis is starting with an investigation of the relation between moisture and differentmechanical properties on a continuum material level, and then these relations are applied onthe packaging design level through experimental testing and simulations. In Paper A, a material characterization was performed on a series of five paperboards withdifferent grammages from the same producer. Five types of mechanical tests to characterizethe paperboards’ material properties were performed: • In-plane tensile test, • Out-of-plane tensile test, • Short-span Compression Test (SCT), • Bending stiffness test, • Double-notch shear test. All tests were performed at several levels of relative humidity (RH). Linear relations betweenthe mechanical properties normalized with their respective value at 50 % RH and moistureratio were found. Paper B examined whether the linear relationships discovered in Paper A are true also forother paperboard series as well. Therefore, 15 paperboards from four producers wereinvestigated in this study, at the same levels of RH as before. Here, the in-plane stiffnessesand strengths and SCT-values were evaluated as a function of moisture. When also themoisture ratios in the investigated paperboards were normalized, it turned out that allpaperboards followed the same linear relationship between normalized mechanical propertyand normalized moisture ratio. Additionally, a bilinear elastic-plastic in-plane model wasdeveloped, that can predict the stress-strain relation of an arbitrary paperboard at an arbitrarymoisture level, and without requiring any mechanical testing except at standard condition(50% RH, 23 °C). In Paper C, this relation was used to estimate input material parameters for simulating a BoxCompression Test (BCT) at different moisture levels. The result showed that it was possibleto accurately predict the load-compression curve of a BCT when moisture was accountedfor.Som förpackningsmaterial betraktat är pappersbaserade material, som exempelvis kartong,väldigt intressanta material. Utöver att råvaran trä är förnyelsebar finns även många andrafördelar med kartong. Ur ett mekaniskt perspektiv är kartong exempelvis väldigt styv iförhållande till sin vikt och har generellt väldigt hög vikbarhet, vilket båda är egenskaper somlämpar sig väl för en förpackning. En klar nackdel med kartong är dess känslighet för fukt.Fukten reducerar kartongens mekaniska egenskaper, vilket följaktligen leder till attförpackningens prestanda försämras. I den här licentiatavhandlingen undersöktes initialtsambanden mellan fukt och mekaniska egenskaper på materialnivå, för att sedan överförasambanden till förpackningsnivå genom experimentell provning och simuleringar. I Artikel A utfördes en materialkaraktärisering på en kartongserie innehållande femkartonger med varierande ytvikter från samma tillverkare. Fem typer av mekaniska provgenomfördes för att karaktärisera kartongernas respektive materialegenskaper: • Dragprov (i planet), • Dragprov (ut ur planet), • Korta kompressionsprov (SCT), • Böjstyvhetsprov, • Skjuvprofilsprov. Samtliga prov utfördes vid flera olika nivåer av relativ fuktighet (RH). Linjära relationermellan mekanisk egenskap normerad med motsvarande värde vid 50 % RH och fuktnoterades. I Artikel B undersöktes huruvida de linjära sambanden som upptäcktes i Artikel A stämmeräven för andra kartongserier. 15 kartonger från fyra producenter undersöktes därför i dennastudie vid samma fukthalter som tidigare. I den här studien undersöktes endast dragprov iplanet, samt SCT. När även fuktkvoterna i de undersökta kartongerna normerades visade detsig att alla kartonger följde samma linjära relation mellan normerad mekanisk egenskap ochnormerat fuktinnehåll. Utöver detta utvecklades en bilinjär elastisk-plastisk i-planet-modellsom kan prediktera en godtycklig kartongs spännings-töjningsförhållande för godtyckligfuktnivå, utan att någon mekanisk provning utöver standardklimat (50 % RH, 23 °C) behöver genomföras. I Artikel C utnyttjades det linjära sambandet mellan mekanisk egenskap och fuktkvot genomatt prediktera de ingående materialegenskaperna som användes vid simuleringar avboxkompressionsprovning vid olika fuktnivåer. Simuleringarna jämfördes med experimentellprovning och visade sig kunna prediktera experimentella resultat vid olika fukthalter bra.
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Wallmeier, Malte, Marek Hauptmann, and Jens-Peter Majschak. "The Occurrence of Rupture in Deep-Drawing of Paperboard." NC State University, 2016. https://tud.qucosa.de/id/qucosa%3A30057.
Full textAbstract:
The production of paperboard packaging components in fast-running machines requires reliability of the production process. Boundaries for the process parameters and constraints for the geometry of the tools require investigation to determine dependable configurations. This paper aimed to investigate the relationships between process parameters, tool geometry, and the occurrence of rupture in the deep-drawing process of paperboard. Different types of ruptures in various phases of the process were distinguished and linked to their specific cause. An extensive experimental investigation with multiple variables of influence was conducted. A logistic regression model was used to describe the experimental data and was statistically validated. The blankholder force was found to be the most influential parameter. Interactions between the parameters blankholder force, punch velocity, and punch diameter were recognized. A high punch velocity can reduce the probability of rupture when the punch diameter is adjusted.
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Erhage, Sofie. "Optimization of tear strength in a multi-ply paperboard." Thesis, Karlstads universitet, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62638.
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The thesis has been carried out as a part of the Master of Science in mechanical engineering at Karlstads University. The purpose of the study was to evaluate how different variables affect the tearing resistance in a multi-ply paperboard. The paperboard’s final quality is dependent on several different process – and recipe variables and has, in this study, been analyzed with respect to ply grammage, ply composition and refining energies. This was investigated by manufacturing of anisotropic sheets consisting of four plies and isotropic sheets consisting of single-ply sheets. The multi-ply sheets were manufactured where one variable at a time were tested at different values. The single-ply sheets were manufactured of pure pulps with the refining energy being varied. A total of nineteen unique multi-ply sheets and twelve unique single-ply sheets were manufactured. All sheets were tested with respect to the properties including tensile strength, bending stiffness, tear strength and delamination strength. The study shows that an improvement in tearing resistance is obtained when the amount of CTMP-pulp in the center plies 2 and 3 decreases simultaneously as the amount of broke-pulp and unbleached chemical pulp in the same plies increases. The consequence of this improvement is reduced thickness and thereby reduced bending stiffness. The study also shows that several pulps has an optimal degree of refining for maximizing tear strength in paperboard. The major source of error is believed to be the method of manufacturing. It is also possible that the amount of test points has been too few to be able to see any clear trends for several variables.
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Stone, Gregory M. "Beneficial Reuse of Corrugated Paperboard in Civil Engineering Applications." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/691.
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Abstract
Beneficial Reuse of Corrugated Paperboard in Civil Engineering Applications
Gregory Michael Stone
An investigation was conducted to explore the potential for reuse of corrugated paperboard. Corrugated paperboard represents a large fraction of the municipal solid waste generated and discarded in the United States. Alternative applications for reuse can provide a significant benefit by reducing the volume of waste being disposed and by reducing the use of raw materials. Four civil engineering applications were examined for potential beneficial reuse of corrugated paperboard: slurry trench construction, vertical drilling, directional drilling, and controlled low strength materials (CLSM).
For the purpose of this project, corrugated paperboard was pulped and added to bentonite slurry or CLSM mixtures. Bentonite slurry mixtures were tested for viscosity, density, filtrate loss, and permeability. The behavior of the bentonite slurries was greatly influenced by interaction and interlocking of corrugate fibers; in general resulting in increased viscosity, filtrate loss, and permeability and decreased density. CLSM mixtures were tested for flow consistency, unit weight, air content, and compressive strength. CLSM mixtures prepared with corrugated paperboard showed an increased water demand due to high absorption of the corrugate. The higher water content was a significant factor contributing to decreased unit weight and compressive strength. CLSM mixtures containing corrugated paperboard also exhibited increased air contents, possibly due to entrapment of air within the corrugate pulp.
Corrugated paperboard was used to successfully replace up to 27% of bentonite for slurry trench applications, 60% of bentonite for vertical drilling applications, and 59% of bentonite for directional drilling applications while maintaining acceptable engineering properties. For CLSM mixtures up to 1% of fine aggregate was replaced with corrugated paperboard while maintaining satisfactory engineering properties.
Incorporation of corrugated paper board into bentonite slurry, CLSM, and drilling fluid applications provides a viable option for beneficial reuse.
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Johansson, Anton. "Influence of the adhesive on the mechanical properties in laminated multi-layer paperboard : Evaluation of two common dispersion adhesives, their failure modes, internal strength and influence on bending and tensile properties." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-33662.
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The objectives of the thesis were to investigate the adhesives influence on the mechanical properties in laminated multi-layer paperboard. The study also strived to find a method to investigate the interface strength of the adhesive layer. This was investigated by constructing handsheets of laminated paperboard by gluing a bulky, CTMP center ply, Chromofoil, of two different grammages, 290 g/m2 and 360 g/m2, together with two outer plies of ordinary copy paper, Multi- Copy 80 g/m2. The sheets were glued with two types of dispersion adhesives, a starch based adhesive and a polyvinyl acetate based adhesive. Twelve types of test specimens were constructed and tested in a series of mechanical tests, which involved a tensile test, a two-point bending test and a Scott Bond test. The method called “digital image correlation” was used trying to investigate the interface strength of the adhesive layer. The study also involved an evaluation of the possibility to predict the bending stiffness of laminated multi-layer paperboard by using calculations according to classic laminate theory. The results show that it is fully possible to use these calculated values as a prediction, with low risk of overestimating the bending stiffness of the paperboard and without involving the adhesive layer in the calculation. The method provided high absolute values in bending and tensile properties, which increased with increasing amount of glue applied. This came at the cost of grammage, which lead to low index values. The overall conclusion is that the effect from the adhesives is somewhat negative, since the mechanical properties would have been improved if the adhesive had been replaced with more fiber. The major source of errors during the experiments was the roughness of the manufacturing method. This lead to an uncertainty about whether the right amount of adhesive had been applied to the test specimens. Due to this the validity of the results could be questioned. Digital image correlation proved to be a rather sensitive method that requires a high accuracy setup and execution for it to be applicable in this type of study. The failure mode of the glue seam correlated well to the amount of glue applied. A lower amount of adhesive applied increases the likeliness of failure of the glue seam.
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Östlund, Magnus. "Residual stresses in paperboard and the influence of drying conditions." Doctoral thesis, KTH, Solid Mechanics (Div.), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-469.
Full textAbstract:
The drying sequence in the manufacturing process for paperboard involves evaporation of water, primarily from within the fibres. The vapour is then transported out of the web by pressure or concentration gradients. As the moisture transport from the paper web to the ambient is quicker than the moisture transport within the fibre network to the surfaces of the web, moisture gradients develop through the thickness of the web. This work concerns effects on the mechanics of paper drying from the variation in moisture through the relatively thin structures of paper and paperboard.
Distributions of inplane residual stresses through paper materials in the unloaded state after drying are believed to be caused by the varying moisture through the thickness during drying. The distributions in general exhibit compressive stress near the board surfaces and tensile stress in the interior of the board. This may be modified after drying and is also affected by structural variation in the material between different plies of multi-ply paperboards.
The stress development during drying is important because it influences the resulting material properties of the paper and because it can lead to curl, which is a quality problem. The residual stresses themselves are an error source in simulation or evaluation of the mechanical behaviour of paper.
In this work, residual stress distributions in paperboard were determined experimentally, to clarify the mechanisms of residual stress build-up. An experimental method for such tests was also developed. Based on the experimental findings, the mechanics of paper drying was modelled and the stress build-up simulated. Simulation offers a way of studying how the properties of paper develop during drying of wet paper webs.
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Crespo, Juan. "Stiffness Design of Paperboard Packages using the Finite Element Method." Thesis, KTH, Hållfasthetslära (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104824.
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This thesis focuses on FEM analysis of paperboard global stiffness. Simulations in Abaqus and experiments were carried out where the deformation was measured. The experimental results were compared with simulation results in order to verify the FEM simulations. Different types of boxes were used to carry out the empirical experiments. The analyses are based on one model that simulates the mechanic behavior of the used boxes. The influence of the creasing stiffness in the global stiffness is specially analyzed. Different gluing zones, materials and structural geometries were used in boxes. The model predicted the experimental results well except from the gluing zones that in some experiments had a higher impact concluding in worse results. Moreover, the results of the work indicate that the deformation of the boxes mostly depend on the bending stiffness of the paperboard while the influence of the creasing stiffness is low.
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Östlund, Magnus. "Residual stresses in paperboard and the influence of drying conditions /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-469.
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Olsson, Robert. "Some aspects on flexographic ink-paper and paperboard coating interaction." Doctoral thesis, Karlstad : Faculty of Technology and Science, Chemical Engineering, Karlstad University, 2007. http://www.diva-portal.org/kau/abstract.xsql?dbid=1218.
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Müller, Tobias, Alexander Lenske, Marek Hauptmann, and Jens-Peter Majschak. "Analysis of Dominant Process Parameters in Deep-Drawing of Paperboard." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230928.
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The application of the wrinkle measuring method described in Müller et al. (2017) and the subsequent evaluation algorithm of a range of deep-drawn samples were used to determine the influences and interdependencies of blankholder force, tool temperatures, and drawing height on the formation of wrinkles in paperboard. The main influences were identified and quantitatively evaluated. For the given experimental space, a regression function was derived and validated in further experiments. It was shown that a quadratic regression was superior to the previously used linear regression. The findings were discussed and compared with the results of similar experiments from past publications. Special attention was given to the wrinkles formed and the resulting quality of the formed paperboard cups. The restrictions of the data acquisition from the measuring method that was used and limitations of the model were presented to demonstrate the reliability of the results.
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Brugés, Javier Mauricio. "Surface characterization methods for quality assessment of polyethylene-coated paperboard." Licentiate thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-41710.
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In manufacturing processes, the quality of a product often depends on its surface, and careful control of surface properties is critical to meet customer requirements. A thin layer of polyethylene (PE) is applied to paperboard to increase barrier functionality and high optical quality of the product. For PE-coated paperboard, product quality inspection is performed at the end of the manufacturing process by taking a portion of the reel to the laboratory for quality inspection. These associated offline characterization methods are destructive and time consuming and are representative of only a small portion of the product. The overall goal of this thesis is to provide new methods to characterize the Surface properties of PE-coated paperboard. Specifically, to determine imaging techniques for measuring surface parameters that affect its barrier functionality and surface roughness. In this thesis, two methods for surface characterization of PE-coated paperboard are presented to quantify the two most important product-related quality parameters, i.e. barrier functionality and optical quality, which are affected by the presence of defects in the coating and by the surface roughness of the product, respectively. First, a full-Stokes imaging polarimeter (FSIP) is used to detect the presence of PE-coated material and to distinguish between coated and uncoated samples at the pixel level. Second, a three-dimensional scanning electron microscope (3D SEM) is employed to calculate the Surface roughness of PE-coated paperboard. These surface characterization techniques offer an advantage over the industry standard due to the high speed and non-contact nature of the measurement, while increasing the throughput of the sample surface parameters studied. A classification accuracy of 99, 74% is achieved using a FSIP to distinguish between PE- and non-PE-coated paperboard at pixel level. Using the 3D SEM technique to measure the topography of PE-coated samples results in a faster method that is comparable in accuracy to a chromatic confocal microscope (CCM). The surface roughness measured with the 3D SEM differs from the standard method by up to 6% and good agreement with statistical parameters is found. In general, surface analysis of PE-coated is often a complex and difficult task for imaging techniques and suitable methods need to be evaluated for their sensitivity to measure the desired surface parameters. The presented characterization techniques inspect larger areas of PE-coated paperboard compared to current industry standards. These methods provide a quantitative solution for surface characterization to inspect the surface parameters necessary to assure the product’s quality.
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Claesson, Filip. "Analysis of length effect dependencies in tensile test for paperboard." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80410.
Full textAbstract:
Paperboard combined with polymer and aluminium films are widely used in food packages. Paperboard is used for the bulk of the package material, and provides the stiffness. Paperboard is a highly anisotropic material, which is affected by how the fibers are orientated. Most fibers are aligned in the machine direction (MD), which is the stiffest direction, perpendicular is the cross-machine direction (CD) where fewer fibers are aligned, and the thickness direction (ZD) which is considerably weaker than in the MD and CD directions. Continuum models are used to describe the material properties to aid the design of package manufacturing processes. In continuum models there are no inherent length scale effects, and the material behaviour is the same regardless of the geometry. For paperboard there have been experimentally observed effects of the gauge length and width of tensile tests. To calibrate and develop these models it is important to observe which effect is a material property, if there is an inherent length scale, and which properties are from the boundary conditions of the experimental setup. Creasing is a process where the length scale is considerably smaller than at the standard tensile test, where the material deforms plastically to create creasing lines to easier fold the paperboard. The failure properties from standard tensile tests are not a good predictor of failure in creasing, where the length scale is considerably smaller. To investigate if there is an effect of the length scale, as the length gets smaller, tensile tests have been performed at different gauge lengths. The tensile tests were performed with a width of 15mm and the gauge length was varied in the range 3-100mm in MD and CD. The results from the tensile tests were, the failure strain and failure stress increased as the gauge length of the tests specimens decreased, both in MD and in CD. Initial stiffness decreased as the gauge length decrease (more notable in MD), and there was an increase in hardening at large strains with decreasing gauge length (more notable in CD). An analytical calculation of the reduction in measured stiffness as the gauge length get smaller was performed, where the decrease in stiffness deemed to be strongly related to the out-of-plane shear modulus. By fitting the analytical solution the experimental data the shear modulus was approximated to 60MPa. The shear modulus has been measured for the same paperboard to 70±23MPa. Simulations of the tensile tests at 5mm did fit the experimental data when the material model was calibrated from the tensile test at 100mm, except the increase in hardening at large strains in CD. It was noted that it was important to use the shear modulus that was inversely calculated by the analytical calculations to get the right initial slope of the simulations of the 5mm tensile tests. Creasing simulations were performed of a test setup of the creasing procedure. The male die was lowered 0.3mm to perform the creasing, which in the tests setup do not result in failure in the material. From the simulations the stress at the bottom of the paperboard during creasing exceeded the failure stress from the tensile test performed at 100mm. The stress during creasing was biaxial, it has stresses both in MD and CD, with is different compared to the uniaxial tensile tests at 100mm. The stress from the creasing simulation in CD was at a maximum of 40MPa where the 3mm tensile tests in CD resulted in a failure stress at 39MPa. The maximum stress in the MD creasing simulation was 96MPa, where the 3mm tensile test resulted in a failure stress at 69MPa. The properties from a long span tensile test are not good predictors of failure in creasing, where both stress state and length scale are very different. The failure stress at 3mm tensile tests in CD is close to the maximum stress from creasing simulations, and may be a good indication of failure. The 3mm tensile test in MD resulted in a considerably lower failure stress than the maximum stress in the creasing simulations, which indicates that the 3mm long tensile test is not a good predictor of failure in MD for creasing, where the length scale is even smaller.
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Ong, Benjamin. "THE RACKING PERFORMANCE OF PAPERBOARD AND WOOD BASED SHEATHING MATERIALS." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1152192631.
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Rose, Megan. "Packaging and sustainability : a study of a liquid paperboard pack." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5408.
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Includes abstract.Includes bibliographical references.
The liquid paperboard (LPB) supply chain converts coated paperboard into single-use beveragecartons. The packaging industry claims to have engaged extensively with matters of sustainabilityand that it has taken many steps to improve resource efficiency associated with this type of packaging. Yet, the 2011 recycling rate of used beverage cartons (UBCs) in South Africa was 0.9%,implying that significant volumes are going to landfill disposal. UBCs are a source of high quality fullybleached furnish (paper fibres), which are routinely recovered and recycled in many other countries,and this practice has been shown by multiple life cycle assessments (LCAs) to reduce environmentalimpacts. The sustainability awareness of different actors in the LPB supply chain was assessed as the first objective, including both South African and international actors in the comparison. Similarities in sustainability reporting were determined by a content analysis of the annual reports supported by two analyses principled on multi-criteria analysis (MCA). The purposively chosen actors in the LPB supply chain were grouped into three namely, manufacturers, organisations and ‘retailers and brand owners’. An analysis using the three focal issues of the Nampak 2010 sustainability report, namely carbon footprint, recycling and training, as search terms shows variation in focus amongst manufacturers to be as wide as that in the two other groups though Stora Enso (an international manufacturer) is noted as having the having the most similar focus. PACSA is the organisation that has the most similar focus to the three Nampak-identified criteria. The four-criteria principled MCA with LCA as the fourth criterion indicates that Stora Enso has the most similar focus to that of Nampak; PACSA is the organisation that has the most similar focus to the four criteria and also had the most focus similar focus to Nampak for the single criterion of ‘recycling’. It is concluded that sustainability awareness in the LPB supply chain is more nuanced in the international companies (based on the date of first responding, word counts in the reports and use of LCA) but is similar between the three company groups in the supply chain. An LCA is presented in order to investigate whether policy recommendations for further reducing the environmental impacts pf LPB use in South Africa.
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Müller, Tobias, Alexander Lenske, Marek Hauptmann, and Jens-Peter Majschak. "Analysis of Dominant Process Parameters in Deep-Drawing of Paperboard." NC State University, 2017. https://tud.qucosa.de/id/qucosa%3A30665.
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The application of the wrinkle measuring method described in Müller et al. (2017) and the subsequent evaluation algorithm of a range of deep-drawn samples were used to determine the influences and interdependencies of blankholder force, tool temperatures, and drawing height on the formation of wrinkles in paperboard. The main influences were identified and quantitatively evaluated. For the given experimental space, a regression function was derived and validated in further experiments. It was shown that a quadratic regression was superior to the previously used linear regression. The findings were discussed and compared with the results of similar experiments from past publications. Special attention was given to the wrinkles formed and the resulting quality of the formed paperboard cups. The restrictions of the data acquisition from the measuring method that was used and limitations of the model were presented to demonstrate the reliability of the results.
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Skillington, Pauline. "Migration of chemicals through coated paperboard for food contact packaging." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/752.
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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Chemistry in the Faculty of Applied Sciences at the Cape Peninsula University of TechnologyPaperboard made from recycled fibres is being used more frequently in direct food packaging applications, in addition to its use as secondary and tertiary packaging. However, recent research has shown that there is a risk that harmful chemicals may migrate from the paperboard into the food. The simplest approach to reducing the migration of these contaminants is the use of barrier films. The barrier efficiencies of these various films can be examined by means of a migration test into a food simulant, followed by extraction in a suitable solvent. The extract can then be analysed by chromatographic techniques such as gas chromatography mass spectrometry (GC-MS) to determine the concentration of the specific contaminants. However on a production level, the availability of this type of highly specialised equipment is limited. A simple, cost effective method is needed to evaluate the barrier properties to specific chemical contaminants. The Heptane Vapour Transmission Rate (HVTR) test is a permeation test method for use at quality control level to determine barrier properties to the migration of organic vapours. The first part of the study focussed on establishing a universal correlation between HVTR and specific migration of diisobutyl phthalate (DiBP), dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP) that would be applicable to any type of functional barrier. However, experimental data demonstrated this was not possible as the correlation factor linking HVTR to specific migration was largely dependent on the type and morphology of the coating considered. The initial objective of the study was reconsidered in favour of building individual models specific to the nature of the coating and substrate considered. A correlation between HVTR and specific migration of DiBP, DBP and DEHP for a polyvinylidene chloride (PVDC) barrier polymer was constructed by varying the applied coating weight. The vapour transport mechanism for the HVTR test and the specific migration test were found to differ, showing that a direct correlation between HVTR and the specific migration was again not possible. However, an indirect correlation could be made. The HVTR method gives an indication of film integrity, whereas the coating weight could be used as an indicator of the specific migration. The correlation between the coating weight and the specific migration yielded an equation that can be used to calculate the specific migration through the PVDC barrier polymer, provided the quantity of the chemical contaminant originally present in the paperboard was known. This equation was specific to the type of barrier polymer, the specific chemical contaminant as well as the intended shelf-life of the food product to be packaged in the paperboard.
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Brandberg, August. "Insights in paper and paperboard performance by fiber network micromechanics." Licentiate thesis, KTH, Hållfasthetslära (Inst.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260374.
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Fiber networks are ubiquitous due to their low cost and high ratio of mechanical performance to weight. Fiber networks made of cellulose fibers from trees are used as information carriers (paper) and as packaging (board). Often the ideal product is both mechanically sturdy and possible to print on. This thesis investigates the underlying reasons for the mechanical performance of paper and board through the discretization and direct simulation of every fiber in the network. In Paper A the effect of fiber-fiber bond geometry on sheet stiffness is investigated. Many packaging products seek to maximize the bending stiffness by employing stiff outer layers and a bulkier layer in the middle. In bulky sheets, the fibers are frequently uncollapsed resulting in a more compliant bonded segment. Because all the loads in the network are transferred via the bonds, such compliance can cause unexpectedly large decreases in mechanical performance. Although many models have been presented which aim to predict the tensile stiffness of a sheet, these predictions tend to overestimate the resulting stiffness. One reason is that the bonds are generally considered rigid. By finite element simulations, we demonstrated the effect of the lumina configuration on the stiffness of the bonded segment on the scale of single fiber-to-fiber bonds, and that the average state of the fiber lumen has a marked effect on the macroscopic response of fiber networks when the network is bulky, has few bonds, or has a low grammage. Compression strength is central in many industrial applications. In paper B we recreated the short span compression test in a simulation setting. The networks considered are fully three-dimensional and have a grammage of 80 to 400 gsm, which is the industrially relevant range. By modeling compression strength at the level of individual fibers and bonds, we showed that fiber level buckling or bifurcation phenomena are unlikely to appear at the loads at which the macroscopic sheet fails. In paper C, we developed a micromechanical model to study the creation of curl in paper sheets subjected to a moisture gradient through the sheet. A moisture gradient is always created during the printing process, which may lead to out-of-plane dimensional instability. We showed that the swelling anisotropy of individual fibers bonded at non-parallel angles causes an additional contribution to the curl observed on the sheet level.Examinator: Professor Mårten Olsson, KTH, Stockholm
QC 20190930
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Bohlin, Erik. "Optics of coated paperboard : Aspects of surface treatment on porous structures." Licentiate thesis, Karlstads universitet, Avdelningen för kemiteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-6721.
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Calendering of coated and uncoated paper is widely used to enhance optical properties such as gloss and print quality. The aim of this thesis is to characterize coatings and prints, and to validate models using experimental results from optical measurements of physical samples. Calendering of coated paper often leads to a brightness decrease. The mechanism for this is not altogether clear. One common explanation is that the porosity of the coating layer decreases and hence the scattering decreases. By comparing simulated and measured results it was shown that modifications of the surface properties account for the brightness decrease of ground calcium carbonate coated substrates with calendering. Monte Carlo light scattering simulations, taking into account the measured decrease of surface microroughness and increased effective refractive index, showed that surface modifications accounted for most of the observed brightness decrease of the ground calcium carbonate coated substrate, whereas the bulk scattering and absorption coefficients were not affected by calendering. It was also shown that the scattering coefficient is significantly dependent on the coat weight whereas the physical absorption coefficient is not. The penetration of ink in the z-direction of a substrate influences the quality of the print. The ink penetration affects print density, mottling and dot gain, common print effects that influence the preference of consumers. The pressure in the printing nip and the porosity of the substrate both affect the amount of ink that is pressed into the porous structure of a coating layer during printing. By printing pilot coated paperboard with different coating porosity and measuring the resulting optical properties of the prints, a basis for simulations of the different layers, that is to say the coating, the print and the mixed layer in between, was created. Results show that ink distribution is strongly affected by the roughness of the substrate. Fibres and fibre flocks underneath the two coating layers created an unevenly distributed coating thickness that affected the print quality. Differences in pore size and pore size distribution also affected the behaviour of the ink. A coating layer of broad pigment particle size distribution resulted in a relatively low print density, in comparison to coatings of narrowly distributed particle sizes. Comparison of dot gain showed that the coating layer of a narrow particle size distribution had a relatively low dot gain compared to others. In this work, these results are explained by the differences in ink distributions on and in the coating layers.
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Hauptmann, Marek, Sebastian Kaulfürst, and Jens-Peter Majschak. "Advances on Geometrical Limits in the Deep Drawing Process of Paperboard." NC State University, 2016. https://tud.qucosa.de/id/qucosa%3A30229.
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The geometrical limits of the deep drawing process of paper to advanced shapes are not known. This report examines the technological limits of convex elements of the base shape in relation to the drawing height and shows the material behavior in the bottom radius of 3D shapes with regard to special material properties. In the bottom radius, non-compressed wrinkles occurred due to the in-plane compression, but wrinkles were reduced by an increased blank holder force or tool temperatures and improved extensibility or in-plane compressive strain. The forming ratio during deep drawing (drawing height related to base diameter) was increased to a value of more than 1 by a blank holder force, which increased with the drawing height such that the initial blank holder force was reduced concurrently. Straight sections in the base shape reduced the risk for ruptures in the edge radii of rectangular shapes, producing a forming ratio in these radii of 2.5. The forming ratio was further supported by a pattern of creasing lines at the blanks with a radial orientation and a number near the expected maximum number of wrinkles. The spring-back at rectangular shapes mainly depended on the drawing height and edge radius.
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Vandenbossche, Sacha. "Prediction of paperboard thickness and bending stiffness based on process data." Thesis, KTH, Hållfasthetslära (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-258827.
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Bending stiness is one of the most important mechanical properties in paperboard making,giving rigidity to panels and boxes. This property is currently only possible to measure bydestructive measure o the production line. The current quality control method is decient byassuming a non-realistic consistency of the paperboard properties along the machine direction.The objective of this thesis is to predict the thickness and bending stiness of the nal boardsfrom process data.Two modelling approaches are used: the rst model calculates the bending stiness from acalculated thickness, while the other one uses the measured baseboard thickness. Both modelsuse common inputs such as material properties and grammage measurement. The grammage istaken from the online baseboard measurement. The material properties come from laboratorymeasurements and assumptions. It is assumed that the density ratio between the outer andmiddle plies is constant for all product lines, at all times. The TSI of each ply is dened fromtensile testing experiments and nominal bending stiness. It is also assumed that the coatingdoes not contribute to bending stiness. The two models use equations based on laminatetheory assuming orthotropic layers and neglecting the interlaminar shear forces. The modelsuse data of two dierent natures: i.e. laboratory data and online data. Laboratory data is usedas a comparative to evaluate the models' performance of calculated values from online data.The results show various levels of prediction accuracy for dierent paperboard grades. Theaverage thickness predictions are all underestimations within a 5% error while the bendingstiness estimations vary much more from product to product; varying from 9% underestimationto 32% overestimation. The bending stiness prediction for CD is consistently higher thanfor MD for both models. Most product lines have better results with the calculated thickness,approach 1. The calculated thickness is always underestimated and bending stiness is overestimated,hence the better results with the rst approach.The most important conclusion from the models' results is the spread of laboratory measurements,when compared to the predicted values. The large variation most likely comes fromproduction, implying inconsistencies in the manufacturing process that are not accounted forby the models. These modelling approaches have failed to capture the production variationsbecause of the lack of input parameters.
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Fernández, Olivares Jacobo Luis. "Modeling the impact of wood and fiber traits on the production costs of corrugated containers." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131143/unrestricted/fernandez%5Fjacobo%5Fl%5F200405%5Fms.pdf.
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Thaung, Tolförs Gustav. "Investigating the process parameters that influence the z-strength of liquid paperboard using data mining and machine learning." Thesis, Uppsala universitet, Tillämpad mekanik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447977.
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Parameters affecting the z-strength of liquid paperboard (LPB) has been analyzed and identifiedusing data mining and machine learning on 6 years of operational data from a multi-ply LPB mill, and control and stabilizing of them was proposed. Linear regression models were built for 9 articles with satisfactory results, and whose attributes were further analyzed as the most important parameters for the z-strength. The results show that generally only parameters affecting the weakest position in the paperboard has any influence on the z-strength, with unbleached softwood pulp refining work affecting the strength the most, while bleached hardwood refining work has a lower influence, and refining work of bleached softwood has almost no influence on the z-strength. Among the other parameters shown to influence the z-strength are kappa number, headbox concentration, broke ratio, strength and retention starches, fractionation and degree thereof, and the conductivity of the process water.
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Marko, Lidia S. "Inventory and price forecasting : evidence from US containerboard industry." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/29389.
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Eyre, Michael Reese Kaczor Nancy Ann. "The effect of flexographic printing on the compression strength of corrugated shipping containers /." Online version of thesis, 1990. http://hdl.handle.net/1850/11178.
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Bortolin, Gianantonio. "On Modelling and Estimation of Curl and Twist in Multi-Ply Paperboard." Licentiate thesis, KTH, Mathematics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1504.
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This thesis describes a grey-box model for the dimensionalstability properties (i.e. curl and twist) of the carton boardproduced at AssiDomän Frövi paper mill in Sweden.AssiDomän Frövi AB is one of Sweden major cartonboard manufacturer, and produces some 350000 ton of board peryear.
Curl is defined as the departure from a at form, and it mayseriously affect the processing of the paper. For this reason,customers impose quite restrictive limits on the allowedcurvatures of the board. So, it is becoming more and moreimportant to be able to produce a carton board with a curlwithin certain limits. Due to the economic significance of thecurl problem, much research has been performed to find sheetdesign and processing strategies to eliminate or reducecurl.
The approach we used to tackle this problem is based ongrey-box modelling. The reasons for such an approach is thatthe physical process is very complex and nonlinear. The inuenceof some inputs is not entirely understood, and besides itdepends on a number of unknown parameters andunmodelled/unmesurable disturbances.
One of the main part of the model is based on classicallaminate theory which is used to model the dimensionalstability of multi-ply board. The main assumption is that eachlayer is considered as an homogeneous elastic medium.
The model is then complemented with a sub-model forunmodelled/umeasurable disturbances which are described asstates of a dynamical system, and estimated by means of anextended Kalman filter.
The simulated curvatures show a general agreement with themeasurements. However, the prediction errors are too large forthe model to be used in an effective way, and a bigger efforthas to be carried out in order to improve the physicalsub-models.
A chapter of this thesis discusses the modelling of thewet-end part of the paper machine with Dymola, a modelling toolfor simulation of large systems based on Modelica language.
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Ilomäki, M. (Marko). "Application of fracture mechanics in analyzing delamination of cyclically loaded paperboard core." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514274008.
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Abstract
The primary objective of this work is to study and model the
fracture process and durability of paperboard cores in cyclic loading.
The results are utilized in creating analytic model to estimate the life
time of cores in printing industry. The life time means here the maximum
number of winding-unwinding cycles before the core delaminates. This
study serves also as an example of use of board as a constructional
engineering material.
Board is an example of complicated, fibrous, porous, hydroscopic,
time dependent and statistic material. Different core board grades are
typically made of recycled fibers. The material model in this work is
linear-elastic, homogeneous and orthotropic.
The material characteristics, elastic and strength properties are
studied first. Then the material is studied from the points of view of
fracture and fatigue mechanics. Some of the analysis and test methods
are originally developed for fiber composites but have been applied
successfully here also for laminated board specimen. An interesting
finding is that Scott Bond correlates well with the sum of mode I and
mode II critical strain energy release rates. It was also possible to
apply Paris' law and Miner's cumulative damage theory in the studied
example situations.
The creation of the life time model starts by FEM-analysis of
cracked and non cracked cores in a typical loading situation. The
elastic-linear material model is used here. The calculated stresses are
utilized in analytic J-integral model. The agreement between analytic
and numerical J-integral estimations is good.
The analytic life time model utilizes the analytic J-integral
model, Miner's cumulative damage theory and analytically formulated
Wöhler-curves which were constructed by applying the Paris' law.
The
Wöhler-curves were constructed also by testing cores to validate the
theoretical results. The testing conditions are validated by
FEM-analysis.
The cores heat up when tested or used with non expanding chucks
and a temperature correction was needed in the life time model to
consider this. Also, single or multi crack model was used depending on
the studied case. The calculated and tested durability prediction curves
show good correspondence. The results are finally reduced to correspond
to certain confidence level.
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Bortolin, Gianantonio. "Modelling and grey-box identification of curl and twist in paperboard manufacturing." Doctoral thesis, Stockholm : Department of Mathematics, KTH, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-519.
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