140 



55 



1.80 



1.60 



1.40 



1.20 



1.00 



0.80 



0.60 



0.40 



0.20 



Special Treotment Steel 

 High Tensile Steel 

 Medium Steel 



- Furniture Steel 



- Copper 



0.4 



0.8 



1.2 

 4i 



1.6 



2.0 



2.4 



17 



Figure 45 - Pressure-Deflection Curves 



The curves plotted are averages of the data obtained on the plates tested. This graph Indicates 



that pressure and deflection can be calculated with rough approximation 



by Equation [19] when z/ a > 0.2 and a = 0.96. 



If the plates tested behaved as ideal membranes, the curves of Fig- 

 ures U5 and '+6 would be straight lines. Pronounced deviations are apparent 

 near the origin, where z/a is small. In this region the actual stresses are 

 far below the ultimate values and the condition of approximately constant ten- 

 sion mentioned on page 42 has not been attained. Consequently relatively less 

 pressure is required to produce a given deflection than is required at higher 

 values of z/a. Beyond this initial region the curves do approximate straight 

 lines. If straight lines are fitted to the curves through the origin, the 

 slopes vary between 0,80 and 1.02; those of the energy curves are generally 



