Experimental plastic loads of cracked plain pipes subjected to internal pressure and bending

Plastic load data from tests on two uncracked and six cracked straight pipes (87.4 mm OD and 4.2 mm thick) are reported. All cracks were internal, and half the thickness deep (a/t = 0.5). Four pipes had short circumferential (2β = 29°) cracks and were tested under moment, pressure or combined steady design pressure and increasing bending. Of the remaining two pipes, one had a short axial crack (2c/a = 12) and the other a long circumferential crack (2β = 150°). Both of these were tested under internal pressure loading. Plastic loads are reported from which it can be concluded that the short cracks have little effect on the plastic load capacity of the pipes. When the defect is long, the usual hoopwise failure under pressure can dramatically change to a circumferential rupture driven by the axial stress. Even for this large defect the failure pressure was well above the pressure level predicted by lower bound limit load considerations.