| Abstract: | Predicting how long time a corrugated board box can be stored with a constant load stacked on top of it without failing is an everyday challenge for a box designer. This is a basic step in corrugated board box material design which is usually resolved by utilizing so-called stacking factors. A stacking factor is the ratio between the compression strength of the box and the stacking load. Higher stacking factors are used to accommodate for longer storing times or high relative humidity conditions. Utilizing stacking factors in the way commonly done today can be a good first approximation. However, this method often neglects or overcompensates for the inherent non-normal distribution statistical behaviour associated with corrugated board box lifetimes. A higher precision in predicting box lifetimes enables material optimization and, thus, a more efficient use of resources. This work presents a convenient way of predicting lifetimes of both containerboards and corrugated board boxes. The approach additionally introduces the concept of reliability into lifetime prediction. The prediction is made directly from material or structural parameters and the applied load. This is accomplished by relating two different parameter sets for the Weibull distribution. It is shown that lifetime is indeed dependent not only on a stacking factor but also on durability and the variations associated with the material or box. |
