Fracture Capabilities in Grizzly with the extended Finite Element Method (X-FEM)

Dolbow, John¹  Zhang, Ziyu¹  Spencer, Benjamin¹  Jiang, Wen¹ 

[1] Idaho National Lab. (INL), Idaho Falls, ID (United States)

关键词: G CODES;    FINITE ELEMENT METHOD;    FRACTURES;    GEOMETRY;    CRACKS;    ALGORITHMS;    MESH GENERATION;    INTEGRALS;    INTERACTIONS;    STRESS INTENSITY FACTORS;    FRACTURE MECHANICS;    PRESSURE VESSELS;    THREE-DIMENSIONAL CALCULATIONS;    SINGULARITY;    REACTOR COMPONENTS Fracture;    Reactor Pressure Vessel;    XFEM;   

DOI  :  10.2172/1244633
RP-ID  :  INL/EXT--15-36752
PID  :  OSTI ID: 1244633
Others  :  TRN: US1601056

美国|英语

来源: SciTech Connect

【 摘 要 】

Efforts are underway to develop fracture mechanics capabilities in the Grizzly code to enable it to be used to perform deterministic fracture assessments of degraded reactor pressure vessels (RPVs). A capability was previously developed to calculate three-dimensional interaction- integrals to extract mixed-mode stress-intensity factors. This capability requires the use of a finite element mesh that conforms to the crack geometry. The eXtended Finite Element Method (X-FEM) provides a means to represent a crack geometry without explicitly fitting the finite element mesh to it. This is effected by enhancing the element kinematics to represent jump discontinuities at arbitrary locations inside of the element, as well as the incorporation of asymptotic near-tip fields to better capture crack singularities. In this work, use of only the discontinuous enrichment functions was examined to see how accurate stress intensity factors could still be calculated. This report documents the following work to enhance Grizzly???s engineering fracture capabilities by introducing arbitrary jump discontinuities for prescribed crack geometries; X-FEM Mesh Cutting in 3D: to enhance the kinematics of elements that are intersected by arbitrary crack geometries, a mesh cutting algorithm was implemented in Grizzly. The algorithm introduces new virtual nodes and creates partial elements, and then creates a new mesh connectivity; Interaction Integral Modifications: the existing code for evaluating the interaction integral in Grizzly was based on the assumption of a mesh that was fitted to the crack geometry. Modifications were made to allow for the possibility of a crack front that passes arbitrarily through the mesh; and Benchmarking for 3D Fracture: the new capabilities were benchmarked against mixed-mode three-dimensional fracture problems with known analytical solutions.