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

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relaxation) occurs and with steady creep the thermal stresses
completely disappear.
Let us examine one of the methods of analyzing disks with
allowance for plasticity - the method of variable elasticity parameters
[7].
Figure 3.58 is a tensile strain diagram. Below the stress
equal to yield point (point a) for most metals there is a linear
dependence between stress a and relative strain c
(3.93)
where E = tg a is the modulus of elasticity of the first kind.
Beyond the yield point (point b) where plastic flow occurs,
stresses can be written by analogy in
the form
a e (3.9941)
where D = tgo is
the modulus of plasticity.
The principal difference between relationships (3.93) and (3.94)
lies in the fact that the modulus cf elasticity E remains the same
for all points of an elastic body and does not depend on the amount
of strain. The value, however, of the modulus of plasticity D
depends on the degree of deformation and, therefore, is differ,,nt
at each point of the zone of the o-c diagram, where plastic flow
occurs.
In the general case of the three-dimensional stress in an
elastic body the following dependence also occurs, analogous to
(3.93):
-.(3.95)
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