Influence of Neutral Axial Stress on Yield and Collapse of Pipe

Axial stress with zero stress as datum is conventionally used in calculating the influence of tension or compression on yield or collapse of pipe. In this paper, zero stress datum is replaced by “neutral” stress datum. This results in a simpler curve of plasticity, namely a circle, instead of the conventional skewed ellipse. Although equations based on neutral axial stress datum are simpler than equations based on zero axial stress datum, the results of the two methods are equivalent for yielding. On the other hand, the results are different for collapse. Experimental collapse pressures are closer to those calculated on the basis of neutral axial stress datum. Means for making allowance for pressures both inside and outside the pipe are given in the paper. Radial stress is taken into consideration, and, therefore, the treatment is triaxial.