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National Advisory Committee for Aeronautics, Technical Notes - Normal Pressure Tests on Unstiffened Flat Plates

Flat sheet panels of aluminum alloy (all 178—T
except for two specimens of Eds-T) were tested under nor—
mal pressures with clamped edge sugports in the structures
laboratory of the Guggenhein Aeronautical Laboratcryr
California Institute of Technology. The thicknesses used
ranged from 0.0l0 to 0.080 inch; the panel sizes ranged
from 10 by 10 inches to 10 by 40 inches; and the pressure
range was.from O to 60~pounds—per—square~inch gage.
Deflection patterns were measured and maximum tensile
strains in the center of the panel were determined by
electric strain gages.

The experimental data are represented by pressure-
strain, pressure-maximum—deflection, and pressure-
deflection curves. The results of these tests have been
compared with the corresponding strains and deflections
as calculated by the simple membrane theory and by large
deflection theories.

P-c primary aim of this research project was the
determination of the deflections and strains in a flat,
unstiffened plate subjected to a pressure normal to its
own plane. Plates were chosen so as to have dimensions
approximating the larger plates on aircraft structures
(since the larger plates usually give more trouble from a
deflection and stress standpoint), and the pressures used
covered the range of pressures found in pressurized cabins
and extended on up into the range of pressures that might
be encountered in fuel tanks and hull bottoms.

Since the membrane theory of plates gives a simple
means of calculating the strains and deflections in a
plate under normal pressures, the exyerimental results
have been compared with the results given by this theory.
In addition, wherever possible, the experimental results
also are compared with theoretical calculations made on
the basis of a large deflection theory which, although
more difficult to calculate, gives more accurate results
for certain ranges of pressures and plate dimensions.
The curves presented, therefore, will give the designer
the probable range of validity of the various methods of
calculation.