FE-analysis of roller creasing of corrugated board

Sammanfattning: Creasing is often performed on paperboard to lower the bending stiffness in a region, making the paperboard easier to fold. Packsize AB uses rolls to crease corrugated paperboard. When using rolls for creasing double-walled corrugated paperboard in the machine direction, fracture occasionally occur on the top liner. This master thesis investigates the initiation of these surface cracks for a BC type corrugated paperboard. Experiments and FE-analysis are performed to study the magnitude of influence for various creasing roll geometries, under various hydraulic base pressures and changes in the material properties. The report includes a discussion of which material parameters that are the most sensitive with respect to surface crack initi-ation. Comparisons between FE-analysis and experiments are made to validate the FE-modeling. The experimental results show that the creasing roll geometries signif-icantly affects the percentage of failure. The best geometry lowered the percentage of failure from 36 % to 0 %. Furthermore, the most sensitive material parameters con-cerning the Tsai-Wu failure criterion used in the numerical simulations are Young’s modulus of the liners and the ultimate strength in the cross direction of the top liner. A variation of 5 % of these material properties yields a change of the maximum Tsai-Wu strength index with 1.5 % and 5 %, respectively. However, further investigations with focus on validation and comparison of FE-analysis and experiments are needed to ensure a reliable model where various types and sizes of corrugated paperboard can be analyzed. This would need measured material properties as a part of the experimental study. Also, the performance of the yielded creasing lines from the experiments are not included in this thesis as well as the criticality of the top surface cracks.