Experimental and numerical investigation of creasing in corrugated paperboard

Creasing is a process which indents a section of corrugated board along fold lines to facilitate a neat fold. The most common failure site in a box made out of corrugated board is at the folds, where the stiffness is reduced by the creasing operation. Crease depth is an important parameter to be controlled. If the crease is too shallow, the section will crack during folding due to excessive strain on the outer liner. On the other hand, if the crease is too deep, the board may crack during the creasing operation itself or it may fail during handling due to excessive reduction in local strength along the fold line. A review of the literature reveals that only a limited amount of research has been carried out on experimental creasing of corrugated boards and comparison with numerical analyses. However, modelling of paper for corrugated board has been successfully done using Hill's plasticity model. In this work, experimental investigations on creasing of corrugated paperboard are carried out. These are complemented by finite element simulations of the creasing process. The simulations are found to be in good agreement with the experimental results. The findings of the work done are helpful in understanding the mechanics of creasing more clearly and in arriving at an appropriate crease depth in order to reduce cracking of corrugated board during the creasing process.