Fracture Behavior and Simulation of X52 Steel Pipe SENT Specimens
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Abstract
Understanding the fracture behavior of pipeline steel is crucial for ensuring the integrity of pipelines in the energy transportation industry. This comprehensive thesis investigates the fracture toughness properties of API 5L AO Smith X52 pipe steel through a combination of experimental tests and numerical analysis. The experimental component of the study utilizes Single-Edge Notched Tension (SENT) specimens to examine fracture behavior. The focus is on assessing critical parameters such as Crack Tip Opening Displacement (CTOD), Crack Mouth Opening Displacement (CMOD), and crack growth length (Δa). To achieve precise displacement measurements in small-sized samples, Digital Image Correlation (DIC) is employed. The establishment of resistance curves (R-curves) for SENT specimens is a key aspect, and the results are used to evaluate the fracture toughness properties, including Force-CTOD, Force-CMOD, CTOD-Δa, and J-Δa curves. The findings reveal consistent fracture behavior across different crack sizes and highlight variations in fracture toughness among different steel grades. This research contributes significantly to the understanding and characterization of pipe steels. In parallel, the numerical analysis component of the thesis employs the Extended Finite Element Method (XFEM) to predict crack initiation and propagation in SENT specimens fabricated from the same API 5L AO Smith X52 pipe steel. Specific fracture parameters, Maxpe and Gc, are used to enhance prediction accuracy. The XFEM models are rigorously compared with experimental results, focusing on Force-CTOD, Force-CMOD, and Force-Global Displacement curves. The study reaffirms the reliability of XFEM in predicting fracture parameters across varying geometries. This research underscores the critical role of fracture mechanics in pipeline integrity assessment and contributes to advancements in fracture behavior analysis for pipeline steel materials. Future investigations are planned to expand the scope of the study by exploring other loading constraints and specimen geometries of the same steel grade.