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

In the examired theory during plastic flow the material is
assumed incompressible; hence it
follows that the Poisson coefficient
P = 0.3 and P = 0.5. Therefore, the dependence of the strain
components on the stress components for a biaxial stressed state
of a disk [see formula (3.70)] can be written in
the form
-. --- (,-...M O,.5)+ at; 00.. (3-99'
Research has established that stresses in
an elasti2 disk when
= 0.3 and )j = 0.5 are virtually identical. Consequently, when
analyzing disks we can use formulas (3.,3) for strains both in plastic
and in elastic regions and, therefore, equations of equilibrium
and strain compatibility are also real for disks which have regions
of plastic flow.
Thus', an analogy has been established between the main equation
necessary for analyzing disks in elastic and elastic-plastic
regions. The principal difference is that when analyzing an elastic
-disk the modulus of elasticity E is known on each radius of the disk
2 and depends only on temperature while the modulus D depends, in
addition, on the value of strain on a given radius, which is not
known beforehand.
Elastic-plastic flow should be analyzed by the method of
successive approximations. For analysis we must have strain curves
similar to the curves in Fig. 3.59 for a given disk material.
Fig. 3.59. Strain diagram for d 20 0 C 300I
23Kh2NVFA (Ei-659) steel. 500
KEY: (1) daN/m 2 . So
(1)
50___600
2- - 700
800oC
0 o005 ,010 ,015 0020 e
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