ON THE LOCALIZATION OF COLLAPSE IN CYLINDRICAL-SHELLS UNDER EXTERNAL-PRESSURE

It is well known that long cylindrical shells used in many practical applications involving external pressure loading collapse catastrophically due to a limit load instability. The limit load is due to interaction between geometric nonlinearities and material nonlinearities due to plasticity. This paper addresses the mechanism of collapse triggered by the limit load instability. It is found that following the limit load the collapse quickly localizes to a section of the shell a few diameters long. The deformations and stresses in the region of localization grow with a decreasing overall pressure whereas the rest of the structure remains intact and retains only a small residual effect from the limit load instability as it unloads. However, under favorable conditions the localized collapse triggers an instability which propagates along the length of the shell and has the potential of catastrophically collapsing the whole structure. The characteristics of the localization are studied parametrically through experiment and analysis.