Prediction for plastic collapse stresses for pipes with inner and outer circumferential flaws

Hasegawa, Kunio; Li, Y.; Mare, V.*; Lacroix, V.*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 5 Pages, 2018/07

Appendix C-5320 of ASME Code Section XI provides a formula of bending stress at the plastic collapse, where the formula is applicable for both inner and outer surface flaws. Authors considered the separated pipe mean radii at the flawed ligament and at the un-flawed ligament and formulas of plastic collapse stresses for each inner and outer flawed pipe were obtained. It is found that the collapse stress for inner flawed pipe is slightly higher than that calculated by Appendix C-5320 formula, and the collapse stress for outer flawed pipe is slightly lower than that by Appendix C-5320 formula. The collapse stresses derived from the three formulas are almost the same in most instances. For less common case where the flaw angle and depth are very large for thick wall pipes, the differences among the three collapse stresses become large.