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

a) b)
c)
Fig. 1.36.
Determining thermal stresses.
Before heating, the part is installed in a rigid housing which
does not allow expansion during heating (Fig. 1.36b).
Reactive
force P occurs during heating. We find it from the thermal
deformation, which is known; for this case it is equal to elastic
deformation: ey = -et = -sAt. Hence P = eyEF.
y
Stresses and strains obtained in
this state differ from actual
ones since there is no rigid attachment of the part. To obtain
true thermal deformations we must apply to the part load P,
which
occurs in the attachment of the part, but is directed in the opposite
direction, i.e.,
with negative sign (Fig. 1.36c).
The sum of part deformations with rigid attachment (Fig. 1.36b)
and deformations from reaction forces P, taken with opposite sign
(Fig. 1.36c), gives tne true elastic deformation. Finally, we
obtain
ey = -uAt+ e(-P) - (1.5?)
This method of finding elastic thermal deformation anu.
consequently, stresses will be used in
even more complex pi-vDlems.
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