The inelastic buckling of varying thickness circular cylinders under external hydrostatic pressure

The paper presents theoretical and experimental investigations on three var ying thickness circular cylinders, which were tested to destruction under e xternal hydrostatic pressure. The five buckling theories that were presente d were based on inelastic shell instability. Three of these inelastic buckl ing theories adopted the finite element method and the other two theories w ere based on a modified version of the much simpler von Mises theory. Compa rison between experiment and theory showed that one of the inelastic buckli ng theories that was based on the von Mises buckling pressure gave very goo d results while the two finite element solutions, obtained by dividing the theoretical elastic instability pressures by experimentally determined plas tic knockdown factors gave poor results. The third finite element solution which was based on material and geometrical non-linearity gave excellent re sults. Electrical resistance strain gauges were used to monitor the collaps e mechanisms and these revealed that collapse occurred in the regions of th e highest values of hoop stress, where considerable deformation took place.