Nonclassical Stability Problems: Instability of Slender Tubes under Pressure

Several nonclassical stability problems dealing with simple cantilever columns of practical engineering importance are comprehensively presented. The salient feature of these rather peculiar problems is that column instability with a tubular cross section filled with a liquid or subjected to gas pressure may occur while its cross section remains axially unstressed. Interesting subcases are also discussed where the static stability criterion of existence of two adjacent equilibria fails to predict the actual critical load. This leads to the erroneous conclusion that the undeformed configuration is the only equilibrium position, being stable irrespective of the level of external loading. Hence, the dynamic stability criterion which is of general validity must be employed for establishing the critical load. It has also been clarified that the hydrostatic pressure load, although nonconstant-directional, cannot be identified as nonconservative.