Mathematical Model
Constitutive equations used to predict the time dependent deformation of materials under constant stress describe the phenomenon known as creep. The Norton Bailey formulation specifically relates the strain rate to the applied load and the elapsed time through a power law relationship. In the packaging industry, this model helps engineers estimate the long term stacking strength of corrugated boxes.
It accounts for the fact that paperboard continues to deform even when the weight remains unchanged.
Stress Resistance
Structural integrity of a warehouse stack depends on the material’s resistance to this slow stretching. The formula uses material constants derived from laboratory testing to forecast when a box might collapse.
Structural Duration
Calculating the life expectancy of a shipping container involves applying the Norton Bailey formulation to various humidity and load scenarios. Because paper is a viscoelastic material, its response to stress is highly sensitive to moisture. The model allows for the adjustment of parameters to simulate the harsh conditions of a supply chain.
Designers use these results to select the appropriate grade of liner and medium to prevent catastrophic failures. This approach reduces the need for expensive over-engineering of packaging. Modern software packages integrate these equations into finite element analysis for more complex container shapes.
Reliable predictions ensure that products are protected without wasting excess fibre.
