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

Total operating time of the sample before -ruptureowas
Let us designate in terms of TlpS t2p, ... , skp the time
intervals necessary for rupture under stresses a, c ""I .2 ak"
These quantities are determined from the stress-rupture strength
curves at various temperatures tl, t 2 , ... , tk. We shall call the
ratios T i/Tlp, T 2 /T2p, ... , Tk/tkp material damage in first, second,
etc., modes,.
Experimental studies on stress-rupture strength of samples
operating under nonstationary stresses and heating have enabled us
to establish the fact that total damage for a given material is equal
to one:
£ s-L-l.(1-31)
This assumption Is called the law of linear damage summation.
Under continu6us stress variation
•P d- .
-- 1,
(1.32)
Where a and t are, subscript and superscript indicating that rupture
time T- i•s determined for •a glvenh dress a and a given temperature
t.
Let us find-the coefficient of operating time reserve,
which, as before, we shall designate nT.
7,7