Main Properties Governing the Ductile Fracture Velocity in Pipelines: A Numerical Study Using an (Artificial Fluid)-Structure Interaction Model

Abstract

Fracture propagation control (FPC) is important in design and operation of pipelines for gas transport. Predicting and understanding the velocity of a running ductile fracture remains as one of the toughest challenges in the fracture research community and is of paramount importance in currently used FPC methods. Current methods use semi-empirical models, based on the Battelle Two Curve Method (BTCM), developed about 40 years ago. However, this approach has shown being inaccurate and unreliable, especially when applied to today's high toughness steels or when non-ideal gases (e.g. CO2 and rich natural gas) are considered. The main reason for this is a poor understanding of the governing factors for the velocity of a running ductile fracture, and represents a huge challenge and source of non-conservatism when applying these mainly empirical tools for ensuring crack arrest. This paper aims to further understand ductile fracture velocity and arrest in pipelines, and to find the main material parameters that control the velocity of a running ductile fracture. A fully coupled fluid-structure interaction framework for modelling a running ductile fracture in a pressurized pipeline have been used to do a systematic parameter analysis of the most important pipeline parameters controlling the fracture velocity.