The failure of torispherical ends of pressure vessels due to instability and plastic deformation—An experimental investigation

Twelve model pressure vessels with torispherical ends have been tested under internal pressure to investigate failure by instability and plastic deformation. The models covered combinations of three head heights and four thicknesses. All the thicker specimens with internal diameter-thickness ratios of 53, 106 and 212 failed by plastic deformation. The three thin specimens with an internal diameter-thickness ratio of 530 failed by buckling of the torus due to the circumferential compressive stresses. The experimental results for limit pressure and instability failure are compared with theoretical values. The effect of change of geometry is significant particularly for the larger head heights. For these specimens the experimental limit pressure is higher relative to theoretical predictions than is the case for the smaller head heights. A simple approximate theory is presented for predicting the pressure at which buckling occurs in the torus. The correlation of the new predictions with the experimental values is not good, but the new predictions are lower than those previously published.