Sinking of hulls – Disparity between theory and experimental results
Instability of shells

The stability of the elastic equilibrium of shells (or other structural components), subjected to loads that cause compressive membrane forces, can be studied by the energy method or by the adjacent-state equilibrium method.

• These methods give the following formula for calculating the critical stress of a thin, perfect cylindrical shell of average length under meridian compression, whose edges are fixed in both radial and circumferential directions during buckling (figure 6 ), if we assume that the slight increase in radius due to the Poisson effect can develop freely before buckling:

  $${\sigma }_{\text{Rcr}}=\frac{E}{\sqrt{3\left(1-{\nu }^2\right)}}\frac{t}{r}=\mathrm{0,605}E\frac{t}{r}$$