Effective Methods to Determine Stress Intensity Factors for 2D and 3D Cracks

Increasing concern for crack assessment in the pipeline industry motivates analysis to quantify the crack driving force, with the linear-elastic fracture mechanics stress intensity factor, denoted K, viable for many vintage pipeline applications. This paper presents a brief review of numerical methods developed for calculating K via the finite element analysis (FEA) as a background to identify the “best” approaches for such purposes. The existing methods can be categorized into three groups: the displacement-based methods, the stress-based methods, and the energy-based methods. The first group involves the displacement extrapolation method, the quarter-point displacement method, and the displacement correction method. The second group involves the stress extrapolation method and the force method. The third group includes the J-integral method, the stiffness derivative method, the virtual crack extension method, the virtual crack closure technique (VCCT) and ABAQUS direct K output method. Based on the review, four methods were selected and evaluated for a central-cracked plate (CCP) specimen based on the FEA calculations via ABAQUS. The “best” methods are then applied in an analysis of K for through-wall cracks in a line pipe — important reference geometry for leak-versus-rupture analysis.