Influence of flaw configuration on the critical strength of a wall-thinned straight pipe

摘要

This study examines the effect of flaw configuration on the internal burst pressure or the limitbending moment of pipes with artificial wall-thinned flaws. The strength evaluation equation fora crack inside a cylinder has been widely applied. However, the following implicit assumptionsnotably exist when applying the equation for planar flaws to situations with non-planar flaws. 1¤The fracture mode of the non-planar flaw under consideration is identical to that of the crack. 2The effect of the parameter of planar flaws on the strength, which is not considered for a crack, issmall or negligible. However, the experimental results from the systematic burst tests on carbonsteel pipes with artificial wall-thinned flaws examined in this study showed that these implicitassumptions may be incorrect. In concrete, regarding a burst test, a fracture mode has not onlyaxial cracking but also circumferential cracking, and the circumferential angle of a flaw has aneffect on the internal burst pressure. Regarding a bending test, a fracture mode has not onlycircumferential cracking but also a collapse, and the axial length of a flaw has an effect on the limitbending moment.