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Design and Stress Analysis of Extraterrestrial ... - The Black Vault

Design and Stress Analysis of Extraterrestrial ... - The Black Vault

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In the calculation the following temperature gradient, will be<br />

encountered: Atc (z), At <strong>and</strong> At., determined according to the<br />

formulas<br />

where At (Z) is the current value <strong>of</strong> the temperature gradient along<br />

a panel cross section;<br />

Atc is the limiting value <strong>of</strong> the temperature gradient along<br />

apanel cross section which, for the problom studied, is identical<br />

on both surfaces (a <strong>and</strong> b) <strong>and</strong> differs only in sign;<br />

At is the total temperature gradient - the difference in temperatures<br />

<strong>of</strong> surfaces a <strong>and</strong> b <strong>of</strong> the panel.<br />

This gradient is easily determined experimentally. <strong>The</strong> strained<br />

<strong>and</strong> stressed state <strong>of</strong> such a panel, free from support or attachment,<br />

is easy to find,<br />

<strong>The</strong> thermal deformation <strong>of</strong> a section is<br />

it(Z<br />

1 _=z-<br />

2 h12 h7<br />

h<br />

Such a panel will be zero since there is no containment by these<br />

deformations (Fig. 4.17b). Obviously, thermal stresses arise when<br />

thermal deformations are contained. Let us examine the extreme case<br />

when-a panel is rigidly attached along the perimeter. In the<br />

attachment reactive moment arises (Fig. 4.17c) C = 0; =-et;<br />

if we equate the known values <strong>of</strong> e <strong>and</strong> et, we obtain<br />

z<br />

a1z<br />

- -<br />

hr<br />

hence<br />

'<br />

459

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