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

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Let us examine the basic design relationships under creep<br />

<strong>and</strong> subsequent rupture.<br />

Any material having the property <strong>of</strong> elasticity <strong>and</strong> creep<br />

can, in the first approach, be represented in the form <strong>of</strong> the<br />

elementary model shot-in in Fig. i.26, <strong>The</strong> model consists <strong>of</strong> two<br />

different types <strong>of</strong> parts connected in !series - an elastic element<br />

having rigidity C <strong>and</strong> a cylinder filled with a viscous liquid which<br />

can overflow through small holes in a piston. Resistance to the<br />

piston displacement is proportional to the speed <strong>of</strong> its disp~acemenv<br />

<strong>and</strong> the coefficient <strong>of</strong> viscous friction a <strong>of</strong> the liquid.<br />

°:i 0•• • 6, body.<br />

Fi.. 1.26,i Model <strong>of</strong> elastic viscous<br />

I<br />

A<br />

<strong>The</strong> displacement <strong>of</strong> point A <strong>of</strong> the element can be made up <strong>of</strong><br />

the displacements <strong>of</strong> the elastic (subscript "I")<br />

<strong>of</strong> the element (subscript "2").<br />

<strong>and</strong> viscou.. part.<br />

For the elas't'.: part <strong>of</strong> thw ,nwio<br />

P P, I<br />

P=:-CXJ' ,; = ;<br />

(the derivative <strong>of</strong> the time function is<br />

For the viscous part <strong>of</strong> the element<br />

designated by tho jxot).<br />

•'.<strong>and</strong><br />

P-=a, 2 ; X 2 - - I or<br />

a P,(i,1.<br />

dX2 dc<br />

afdc<br />

P<br />

2~-' a

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