If a thin-walled, closed-end pressure vessel is subjected to inter-nal pressure P (with radius a and thickness h), find the value of an additional end load f such that \sigma _{\theta \theta }=\sigma_{zz} (cf. Fig. 3.16).
If a thin-walled, closed-end pressure vessel is subjected to inter-nal pressure P (with radius a and thickness h), find the value of an additional end load f such that \sigma _{\theta \theta }=\sigma_{zz} (cf. Fig. 3.16).
From the above results [Eqs. (3.49) and (3.41)], the associated axial and circumferential stresses are
\sigma _{zz}=\frac{Pa}{2h}+\frac{f}{2\pi ah}, and \sigma _{\theta \theta }=\frac{Pa}{h}.
Now, set the two stresses equal (σ_{θθ}=σ_{zz}) and solve for f:
\frac{Pa}{h}=\frac{Pa}{2h}+\frac{f}{2ah\pi }\rightarrow f=Pa^{2}\pi ,which is seen to equal the pressure times the internal projected area over which it acts. FIGURE 3.16 Schema of a small portion of a tube that could be subjected to an internal pressure and an axial force. Note that the 2-D state of stress at a point p depends on the coordinate system of choice.