Collapse of pipes with plain or gouged dents by bending moment

This paper discusses collapse caused by the bending moment of mild steel pipes containing plain or gouged dents.Five laboratory size pipes were machined with their geometry given by the outside-diameter-to-wall-thickness ratio Do/t≅40 and by the length-to-outside-diameter ratio 2L/Do≅12.0. Defects in the first four pipes had the depth-to-wall-thickness ratio e/t≅0.47, the length-to-outside-diameter ratio 2c/Do≅0.25 and the width-to-wall-thickness ratio 2w/t≅0.50. The gouge in the fifth had these ratios given by e/t≅0.23, 2c/Do≅0.81 and 2w/t≅1.20.Specimens were dented with a rigid, hemispherical indenter. The maximum depth of the dent, (δ/Do)max, varied between 0.15 and 0.23. Dented pipes were collapsed by moment loading whilst subjected to constant internal pressure. This was followed by burst tests. Details about modelling of dents, gouges and the associated FE analyses are provided. Good agreement between experimental and numerical results was obtained in the modelling of denting, but agreement was not so good in the modelling of bending. The FE results under-estimated the experimental values of collapse bending moments.