Combined stability of unstiffened cones – Theory, experiments and design codes

Abstract

The elastic-plastic buckling of short and relatively thick unstiffened truncated conical shells subjected to axial compression and external pressure is investigated. This is done using numerical and experimental approach. For the numerical analysis, the finite element code is employed to obtain the domain of combined stability. To validate numerical predictions, thirteen nominally identical laboratory scale cones with 26.56° semi-vertex angle and 3 mm nominal wall thickness with integral top and bottom flanges were CNC machined from 252 mm diameter mild steel billet. Two of the models were subjected to axial compression, with further two subjected to pure lateral external pressure, while the remaining nine cones were subjected to combined action of axial compression and external pressure of different ratio. Experimental results compare well with numerical predictions except for pure axial compression. However, the accuracy of these results is strongly dependent on the approach to modeling of material. Experimental results were compared with predictions of failure loads obtained from ASME code case 2286–2, and with the ECCS design rules for the case of axial compression and lateral pressure.