Buckling under External Pressure of Cylinders with Toriconical or Pierced Torispherical Ends: A Comparison of Experiment with Theory

Abstract

Experimental buckling pressures are given for some thin cylindrical shells closed by two types of end closure. These were (a) unpierced toriconical shells and (b) torispherical shells penetrated by axisymmetric flush cylindrical nozzles. The loading investigated was uniform external pressure and all the shell combinations were machined and stress-relieved. The theoretical elastic buckling pressures corresponding to the above models were calculated using a digital computer program known as BOSOR 3, which is based on the variational finite-difference technique. This program calculates, for perfect elastic segmented shells of revolution, the asymmetric (i.e. with circumferential waves) bifurcation buckling pressures and also the large-deflection axisymmetric collapse pressure. In the asymmetric elastic case, both linear and non-linear pre-buckling stress resultants may be utilized. For the five cylinders with toriconical end closures, the buckling failures were always elastic and the agreement between theory and experiment was good. For the six cylinders with pierced torispherical ends, failure was by asymmetric buckling, in the n = 1 mode. For most of these cases there were significant discrepancies between the experimental results and the predictions of elastic buckling theory. However, better agreement between theory and experiment was obtained when a more recent version of the BOSOR program, which considers elastic/plastic effects, was utilized. Two limited comparisons, which should be of interest to designers, are also given. One comparison deals with the buckling resistance of a cylinder with either a toriconical or a torispherical head; the other considers the effect on the experimental buckling pressure of a cylinder/torisphere combination of piercing the torispherical head.