Cushion Curves for Impact Response

The integral U((7m) represents the area under the engineering stress-strain master curve up to the maximum stress (7. The static stress is a function of the energy density function U( Jm) - 

The maximum product acceleration G, which occurs when the foam compressive stress has its maximum value is given by  

The parameters C7j and G of the cushion curve can be calculated from the energy density function [/(c7 ,), using Equations (13) and (14). These equations only contain the ratio t/h of the foam dimensions, so the resulting cushion curves can be labelled with the reduced foam thickness = t/h. 

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