Crack Growth Modeling and Constraint Behavior Observations in Complex Crack Geometries

Abstract

The area of complex cracking in piping components and its effects on the fracture behavior and leak-before-beak evaluations has been highly researched. Several researchers have conducted experiments to quantify the behavior through complex cracked piping experiments starting from the 1980s and also more recently in dissimilar metal welds (DMWs). The area has also seen several contributions on the modeling aspects to characterize the crack initiation as well as the ductile crack growth behavior. In this work, the crack growth in complex-crack geometries is revisited through a novel laboratory specimen model, developed by modifying a Single-Edge Notch Tension SEN(T) specimen that is routinely used to obtain the fracture toughness values for both crack initiation as well as crack growth/tearing behavior. Details on the cell size used in the finite element analysis (FEA), and the effects on the predictability of the experimental observations are highlighted. The effects of constraint based on the relative levels of complex-cracking (aspect ratios) are discussed. While the results are precursors to the understanding of the correlations of constraints and fracture for these complex-cracked geometries, they provide guidelines for path forward towards development of methodologies to treat these when making reliable comparisons between material fracture resistance and crack driving forces that are routinely employed in fracture-based leak-before-break assessments for piping and piping components.