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A method for extracting delaminationzones and deformation quantities ofpaperboard during folding (En metod för extraktion av delamineringszoner och deformationsegenskaper hos kartong vid vikning)
This study has been conducted at Tetra Pak to study deformation in liquidpackaging paperboard during the folding process.When a package is formed in the filling machines, the paperboard is foldedaccording to the crease lines. It is of great interest to study the folding processsince it is crucial to the final quality of the package. Mathematical models areused for simulation of paperboard but they require real world measurementsand data for calibration and verification.A method utilizing the optical flow in video sequences of the folding pro-cess of paperboard, which captures the geometrical changes that the materialundergoes during folding, has been developed. Fields such as displacement,deformation gradient, strain tensor, the Jacobian of the deformation, and oth-ers, can be obtained for actual paperboard samples. Furthermore, delamina-tion zones and openings in the paperboard can be obtained automatically. Allmetrics and quantities can be given as a function of time, or folding angle,allowing for study of the translation and propagation of these.The method has been verified by applying it on rendered simulations ofthe folding process, of which ground truth data is available.Quantitative and qualitative analyses have been performed on video se-quences of the folding process of paperboard. The most relevant quantities,fields, and metrics have been extracted for all samples. An analysis of delam-ination zone area as a function of folding angle has also been conducted.
Magnus Oskarsson, Centre for Mathematical Sciences, Lund University,Eric Borgqvist, Johan Tryding Tetra Pak
Kalle Åström, Centre for Mathematical Sciences, Lund University