A two-curve model for crack arrest prediction of high-grade pipeline based on Crack Tip Opening Angle

Abstract

The core of arrest control for natural gas pipelines is the prediction of crack arrest toughness. Relevant studies have shown that the Battelle two-curve model (BTCM) which is based on Charpy impact toughness is no longer applicable for high-grade pipelines with high strength and toughness. Thus, it is urgent to establish a new prediction model for crack arrest based on a more appropriate fracture parameter. In view of this, the Crack Tip Opening Angle (CTOA), which has a wide application prospect, is selected as the arrest toughness parameter to modify the BTCM. Firstly, based on the previous work, an analytical model of crack arrest pressure based on CTOAC is established with the energy balance theory. Then, the relationship between crack tip pressure and crack velocity under different conditions is explored with the help of the numerical simulation method for dynamic crack propagation in pipelines. Finally, based on the above results, the BTCM is modified to form a novel two-curve model taking CTOAC as the parameter to characterize the crack arrest toughness. The results for the proposed CTOA-based two-curve method (CBTCM) are discussed and compared with those obtained by well-established methods such as BTCM, HLP and HLP-Sumitomo models. The work in this paper provides a new reference for fracture control of the high-grade pipeline.