2023 Validation of Fatigue Crack Growth Modeling Solutions using Measurements Collected on API X65 Piping Specimens

Point of Contact(s): Adrian Loghin, Jim Harter

Abstract: Building confidence in different modeling techniques to assess damage tolerance capabilities of components under service conditions relies on a continuous verification and validation effort. The verification benchmarking (usually conducted for mode I stress intensity factors, KI) is accomplished by comparison against analytical or high-resolution numerical solutions while for the validation task, lab-controlled experimental measurements (i.e., crack size vs. cycles) are used as a reference for a complete remaining useful life solution. Different mechanical testing conditions and multiple specimens are often considered to capture experimental variability and provide a large set of measurements that can be used for numerical solution validation and uncertainty quantification. Four fatigue crack growth experimental measurements were used as a validation reference set for an incremental 3D FE modeling procedure and for a reduced order model-based application. The test procedure consists of a four-point bend 5L X65 pipe specimen subjected to two repeating R-ratio constant amplitude loading blocks to allow formation of beach marks that can be used post-failure to identify crack size and shape during the experiment. The two modeling processes capture all details related to experimental procedure: overall geometry of the specimen, crack location and orientation, two constant amplitude loading blocks: 10000 cycles performed at a stress ratio of R=0.1 followed by 5000 cycles at R = 0.5. Fatigue crack growth rate data provided by BS 7910 was used to obtain the 3D FEM based explicit crack growth solution as well as the equivalent solution using the reduced-order model. Digitized post-failure beach mark data was used as a reference to validate against the crack fronts generated in the numerical solution for each loading block. Fatigue crack growth rate uncertainty within the bounds provided by BS 7910 is considered in this validation benchmarking.

Data that is made available: “individualP11 - forERSI.xlsx” = digitized markers along with the numerical solutions for specimen marked PE-1-1 “individualP12 - forERSI.xlsx” = digitized markers along with the numerical solutions for specimen marked PE-1-2 “individualP31 - forERSI.xlsx” = digitized markers along with the numerical solutions for specimen marked PE-3-1 “individualP22 - forERSI.xlsx” = digitized markers along with the numerical solutions for specimen marked PE-2-2

Reference Adrian Loghin, James Harter, Validation of Fatigue Crack Growth Modeling Solutions using Measurements Collected on API X65 Piping Specimens, PVP2023-101256, ASME PVP Proceedings, 2023. Reference for the experimental measurements used in the validation: Li, Z, Jiang, X., Hopman, H, Liu, Z., An investigation on the circumferential surface crack growth in steel pipes subjected to fatigue bending, Theoretical and Applied Fracture Mechanics, pp. 205, 2020.