Crack initiation, crack growth and fracture behaviour of large diameter pipes with circumferential defects under internal pressure and superimposed alternating bending load

Abstract

Pipes made of steel 20 MnMoNi 5 5 and MnMoNiV-special melt having an external diameter of 800 mm, wall thickness of 47 mm, and length of up to 5500 mm were provided with circumferential defects of defined length and depth. They were loaded by internal pressure and a superimposed alternating bending moment. During the tests deformation and crack growth were determined in the wall thickness and circumferential direction. Pipes with an outer diameter of 226 mm and a wall thickness of 20 mm were used to investigate the leak-before-break behaviour in the dynamic sphere. These pipes were also made of steel 20 MnMoNi 5 5 and a MnMoNiV-special melt and were loaded with internal pressure and an alternating bending moment. The excitation took place at the resonance frequency of the pipes. The pipes also contained circumferential defects of defined length and depth.