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2p
or   . (9.20)

1 c 2
If you want to choose the size of the cylinder, it is one of the
largest wondering radii ratio and r r , from equation (9.20) can
1 2
determine the required size of the second
radius of the cylinder.
0
From this formula it is clear that even with respect to r r 
1 2
(outer radius infinitely large), we cannot allow the cylinder
 
pressure more than 0,5  .
Thus, the increase in outer radius of the cylinder at high thickness
of the wall has little effect on increasing its strength.

Questions for self-assessment

1. What is shell?
2. What is called the median surface of the shell?
3. Under what conditions is a shell considered to be thin-
walled?
4. What membranes are called the axisymmetric?
5. Describe Kirchhoff – Ljva’s hypothesis.
6. Under what conditions is a membrane stress state
considered to be momentless?
7. Why is momentless stress state more favorable than
moment stress state?
8. Deduce Laplace’s equation.
9. What equation is taken to Laplace’s equation for
finding the circular and longitudinal stress?
10. What material is strained for state thin-walled vessels
that loaded with internal pressure?
11. How do you calculate the strength of thin-walled
axisymmetric shell?
12. Write the conditions of strength for thin-walled shell
of III-S and IV-S theory of strength.

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