Experimental and Numerical Study on LCF Crack Propagation of Coiled Tubing Steel

Authors

  • Jijia ZHONG Southwest Petroleum University; Sichuan Aerospace Zhongtian Power Equipment Co. Ltd
  • Guanghui ZHAO School of Mechanical Engineering, Southwest Petroleum University
  • Litong WANG Southwest Petroleum University
  • Yi HE Southwest Petroleum University
  • Sihai HU Southwest Petroleum University

DOI:

https://doi.org/10.5755/j02.mech.31056

Keywords:

coiled tubing (CT), low-cycle fatigue (LCF), crack growth rate, experimental study, J-integral.

Abstract

Coiled tubing (CT) is a joint-less long oil pipe that is wound around a reel and can be run and pulled continuously. Due to the particularity of the operating process, low-cycle fatigue (LCF) failure of the CT constitutes the main production cost. Aiming at the characteristics of small diameter and thin wall of CT, a single-edge-notched (SEN) arc specimen was designed and machined. LCF tests were conducted with force-controlled mode. Cyclic softening of the CT steel was presented and crack growing rates were measured. Meanwhile, finite element simulation was carried out to obtain the relationships among J-integral, crack size and load. Based on the experimental and numerical results, the speed of the LCF crack growth of the CT steel is expressed as an explicit function of the J-integral. It provides a basis for predicting the LCF life of the CT under working conditions from the perspective of crack propagation.

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Published

2022-10-21

Issue

Section

MECHANICS OF SOLID BODIES