CRACK-GROWTH AND FRACTURE-BEHAVIOR OF PIPES WITH CIRCUMFERENTIAL DEFECTS UNDER INTERNAL-PRESSURE AND SUPERIMPOSED ALTERNATING BENDING LOAD

Pipes made of 20 MnMoNi 5 5 steel and an MnMoNiV special melt, with 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 len gth and depth. The pipes were loaded by internal pressure and a superi mposed alternating bending moment. During the tests, deformation and c rack growth were determined in the wall thickness and circumferential direction, and these were compared with calculated values. 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. Th ese pipes also were made of 20 MnMoNi 5 5 steel and an MnMoNiV special melt, and were loaded with internal pressure and an alternating bendi ng moment. The excitation took place at the resonance frequency of the pipes. The pipes also contained circumferential defects of defined le ngth and depth.