Box Crush Test and the Chalmers DST
Ian Chalmers January 2015Click here to download a copy of this paper in PDF format.
Can MD Torsional Stiffness be used to calculate BCT?
Figures 1, 2 and 3 show very strong relationships between board crush BCT and MD Torsional Stiffness. So yes MD Torsional Stiffness can be used to estimate BCT but only on a box by box type basis. Every box will have its own BCT vs MDTS relationship depending on flute type and box dimensions. So you can not develop an accurate single model for BCT vs MDTS unless you have a very powerful “Finite Element Analysis” model then tested on a huge database that incorporates many material properties and box design criteria. It may be possible to obtain enough Empirical data to factor in MDTS into McKee’s BCT equation. But whatever the outcome, with all things being equal, the box with the highest MDTS will always have the highest BCT. The MDTS can be considered to be a degradation factor where the percent loss in MDTS compared to best attainable will predict a boxes BCT. The factor may not be linear.
Crush versus board and box properties
Figure 5 shows a summary of how corrugated board crush effects board and box properties. The least affected property is caliper and the most affected property is box compression performance in the service environment as simulated by cyclic humidity compression creep testing. The best property to measure crush received is MDTS which is the most sensitive property affected by crush.
Figure 5: Percent crush versus board and box properties from Chalmers (Appita 2007)
