DYNAMICS OF PACKAGE CUSHIONING 



403 



pended mass exceeds the total weight of the package. It was not necessary 

 to distinguish between maximum acceleration on the first downstroke and 

 first upstroke, since these are the same when there is no damping. With 

 damping, however, the maximum acceleration on the first downstroke is 



1.0 



Fig. 2.6.1 — Influence of velocity damping on maximum upstroke acceleration. See 



equation (2.5.5). 



greater than that on the first upstroke (Fig. 2.5.2) and it is the latter that 

 controls rebound. Hence damping inhibits rebound. 



For example, with 50% of critical damping ((82 = 0.5), equations (2.5.8) 

 and (2.5.9) and Fig. 2.5.2 show that for the first downstroke Gm/Go = 1 

 while for the first upstroke G,n/Go = 0.164. Hence the tendency to rebound 

 is reduced by a factor of six when damping to the extent of 50% of critical 

 is added to an undamped package. 



The ratio of the maximum acceleration on the first upstroke to the maxi- 

 mum undamped acceleration is plotted in Fig. 2.6.1 for various values of ^o . 



