The mechanism of failure in bending of paperboard

Carlsson, Leif A.; Fellers, Christer; Ruvo, Alf de

doi:10.1007/bf00550769

Cited by 12 publications

(15 citation statements)

References 4 publications

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“…One such technique is the short-span compression test (SCT), where a short sample of the paperboard is compressed. The failure strength in this test, the SCT value, is considered to be an important measure for, for example, the foldability of the material, see Cavlin 1 and Carlsson et al, 2 and the box compression strength, cf. Ristinmaa et al 3 However, the deformation mechanisms that are active during this test have not yet been fully understood.…”

Section: Introductionmentioning

confidence: 99%

Localized Deformation in Compression and Folding of Paperboard

Borgqvist

Wallin

Tryding

et al. 2016

Packag. Technol. Sci.

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The localized deformation patterns developed during in-plane compression and folding of paperboard have been studied in this work. X-ray post-mortem images reveal that cellulose fibres have been reoriented along localized bands in both the compression and folding tests. In folding, the paperboard typically fails on the side where the compressive stresses exists and wrinkles are formed. The in-plane compression test is however difficult to perform because of the slender geometry of the paperboard. A common technique to determine the compression strength is to use the so-called short-span compression test (SCT). In the SCT, a paperboard with a free length of 0.7 mm is compressed. Another technique to measure the compression strength is the long edge test where the motion of the paperboard is constrained on the top and bottom to prevent buckling. A continuum model that previously has been proposed by the authors is further developed and utilized to predict the occurrence of the localized bands. It is shown that the in-plane strength in compression for paperboard can be correlated to the mechanical behaviour in folding. By tuning the in-plane yield parameters to the SCT response, it is shown that the global response in folding can be predicted. The simulations are able to predict the formation of wrinkles, and the deformation field is in agreement with the measured deformation pattern. The model predicts an unstable material response associated with localized deformation into bands in both the SCT and folding. the machine direction (MD), and the transverse direction to MD is known as the cross direction (CD). The failure stress in ZD is typically two orders of magnitude smaller than the failure stress in MD, while the failure stress in CD is about two to three times lower than MD. To obtain a low weight, paperboard is commonly produced as a sandwiched structure, with stronger mechanical properties in the outer-plies (top and bottom) and weaker properties in the middle. Measurements and simulations have been performed for a single-ply board in this work.Good foldability implies minimum spring back and absence of cracks along fold lines, cf. Cavlin. 1 Because of the bending state present during folding, in-plane compression strength has been attributed for being the dominant factor affecting the foldability of paperboard. The SCT value multiplied with the thickness is shown to be correlated to the maximum bending moment by, for example, Edholm. 4 However, later investigations have confirmed that the out-of-plane shear is an important mechanism to consider during converting procedures, cf. Nygårds et al., 5 Beex and Peerlings, 6 and Borgqvist et al. 7 The in-plane compression strength is difficult to measure because of that structural instabilities (buckling) easily are triggered as a result of the slender geometry of the paperboard. To overcome the difficulties associated with the structural stability in compression tests, short-span length can be used to prevent the buckling. An alternative experimental method is ba...

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Section: Introductionmentioning

confidence: 99%

Localized Deformation in Compression and Folding of Paperboard

Borgqvist

Wallin

Tryding

et al. 2016

Packag. Technol. Sci.

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“…3 A corresponding tensile strain is induced in the convex parts of the bent structure, but since the cellulose structure cannot withstand as large an in-plane strain in compression as in tension, 4-6 the in-plane compressive strain induced by bending is able to break/delaminate the structure without any great risk of tensile failure. Shear strain and stress are also coupled to local bending of the structure but, as has been shown by Cavlin et al 4,7 such stress or strain, even if it is considerable, has no significant effect on the creasing point. Paperboard structures actually start to yield or break by in-plane compression at a strain between 0.1 and 0.5%, while the corresponding range in tension is between 0.3 and 2% 4, 6 and the critical shear strain is much higher, probably 10-30 times higher.…”

Section: In-plane Compressive Stress -The True Creasing Factormentioning

confidence: 91%

“…Paperboard structures actually start to yield or break by in-plane compression at a strain between 0.1 and 0.5%, while the corresponding range in tension is between 0.3 and 2% 4, 6 and the critical shear strain is much higher, probably 10-30 times higher. 3,[7][8][9] During the folding operation the various parts of the creased zone, as appears in Figures 1-3, cooperate effectively to reduce the folding resistance, the parts are enlarged as folding proceeds, approach each other and are finally integrated by the delamination mechanism.…”

Section: In-plane Compressive Stress -The True Creasing Factormentioning

confidence: 99%

“…It has been shown that the breaking level of uncreased paperboard is very strongly related to the compressive strength of the board. 3,[7][8][9] In fact, it has been shown that the bending strength can be considered as a measure of the in-plane compression strength of paperboard. 3,[7][8][9][10] Superimposed shear stress and strain in the folding zone during folding have no significant effect, 3, 7-9 on either the yield point of the curve or later parts of the curve where significant delamination and buckling out of the structure takes place.…”

Section: Folding Curve and Creasing Effectsmentioning

confidence: 99%

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Creasability testing by inclined rules — a base for standardized specification of paperboard

Cavlin¹,

Dunder²,

Edholm³

1997

Packag. Technol. Sci.

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In die cutting manufacture of paperboard it is necessary to apply the correct creasing conditions, e.g. neither too small nor too big a rule height, in order to achieve sufficiently low folding resistance without any cracks along the folding lines. The most appropriate rule height for a given paperboard is usually determined by trying different rule heights in a series of very time consuming and costly trial and error tests. And, in practice, this procedure must be repeated for each major change in board quality. This report shows that an inclined crease rule, i.e. a rule having a gradually increasing rule height, can be used advantageously to rationalize such tests and to achieve much greater reliability. A folding line produced by such an inclined rule contains both the upper limit for the rule height, i.e. where cracks start to appear, and the lower limit, i.e. where the rule height is obviously too small, and the technical range for achieving a good creasing result is thus clarified in one single test. Illustrative data for two types of paperboard are given as well as some theoretical aspects of the concept of creasability. Considering that the described method not only rationalizes the testing work but also enables more reliable observations to be made than have been possible in the past, the method opens new potentials for effective research and development in the fields of converting, convertibility, die form design, etc. © 1997 John Wiley & Sons, Ltd.

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“…So it is desirable to minimize unnecessary bending. Minimum radii of curvature for multi-ply boards having mass densities of 590, 700, and 760 kg/m 3 have been measured as 60, 40, and 30 mm, respectively for MD bending [26,28]. Based on these values, the radius at failure of the material used in the present study was estimated as 55 mm.…”

Section: Materials Failurementioning

confidence: 97%

Role of simulation in predicting the effect of machine settings on process performance in the packaging industry

Sirkett

Hicks

Singh

et al. 2007

Proceedings of the Institution of Mechanical Engineers, Part E:

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Recent European Union regulations on packaging waste have resulted in a trend towards light-weighting and greater use of recycled materials in the packaging of consumer goods. This has impacted particularly upon the folding carton industry, and has necessitated greater fundamental understanding of the machine-material interactions that take place during carton production. One way to achieve this is through the use of simulation models. Such a model has been created to simulate the behaviour of a folding carton during the critical transition between flattened and erected states. The model is able to simulate process failure (buckling) and investigate the effect of changes in pack, process, material, and tooling parameters. The model is applied here to investigate the effect of variation in two key machine settings. These are the relative orientation of tooling, and the contact points between tooling and carton. The results of the simulation reveal a strong correlation between theoretical and practical results, and as a consequence provide a means for determining the optimum tooling position(s). The study demonstrates the ability of simulation to support the set-up and operation of complex packaging machinery. It is arguable that such tools will be essential for machinery and consumer goods manufacturers to compete in today's highly competitive global markets where quality, efficiency, and flexibility are critical.

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The mechanism of failure in bending of paperboard

Cited by 12 publications

References 4 publications

Localized Deformation in Compression and Folding of Paperboard

Localized Deformation in Compression and Folding of Paperboard

Creasability testing by inclined rules — a base for standardized specification of paperboard

Role of simulation in predicting the effect of machine settings on process performance in the packaging industry

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