摘要：It was well known that CT (Coiled tubing) worked under severely plastic deformation and was used widely in the oil field with its special advantage. Under the interaction of bending, axial loads and internal pressure, especially over 20 MPa the growth of diameter was quick and the deformation of the pipe was serious which would lead to the incompatibility failure, or the accidents resulting from the mechanism declining. So the study on the sectional deformation of the pipe during severely plastic deformation was very important for the safety operation. In this study, the full-scale fatigue experiment was subjected on the fatigue machine of CT under different internal pressure and the testing experiment of diameter was carried on. The variation and distribution of the growth of the diameter to CT along the bending board were discussed which would provide reliable basis for judging the dangerous place and the stress concentration area. The laws of the growth ratio of the maximum diameter during the fatigue deformation were found which could evaluate the degree of the deformation. And the real-time monitoring of diameter could predict the remaining life.
