ACCURATE 4 FULL CRACK CRACK
(If the material is elastic-plastic, the size of the circular partition should generally contain the plastic zone and allow a number of the contours for the contour integrals to enclose the plastic zone while still remaining in the elastic region.) The remaining partitions are created so that the element shapes satisfy the element quality criteria in the regions away from the crack tip. When the deformation and the material are linear as in this example, the diameter of the circular partition used to map the crack-tip mesh for contour integral calculations is not critical. Engineering judgment is required to establish adequate mesh refinement to produce contour-independent results while avoiding the possibility of creating elements at the crack tip that are so small in relation to other elements that they introduce numerical conditioning issues and associated round-off errors. The accuracy of the contour integrals is not very sensitive to the biasing. In the circular partitioned region surrounding the crack tip where the contour integrals are calculated, the mesh should be biased moderately toward the crack tip. In the three-dimensional cases the corresponding partition is a curved tubular volume enclosing the crack tip.Ī refined mesh at the crack tip is required to obtain contour-independent results i.e., there is no significant variation in the contour integral values calculated for successive rings of elements around the crack tip. In the axisymmetric cases a circular partition is created to mesh around the crack tip. To be used for the evaluation of contour integrals, the mesh around the crack tip must be modeled as described in Modeling fracture mechanics, Section 20.1 of the ABAQUS/CAE User's Manual. The models use either quadrilateral or brick elements with a collapsed side to create triangular elements for two-dimensional cases or wedge-shaped elements for three-dimensional cases, which introduce a singularity at the crack tip. The geometry is partitioned to map rings of elements around the crack tip for the contour integral calculations. The mesh includes a seam along the crack with duplicate nodes, which allow the crack to open when loaded. “Fracture mechanics,” Section 7.10 of the ABAQUS Analysis User’s Manual, provides detailed information on fracture mechanics procedures. Axisymmetric and three-dimensional cases are provided with and without submodeling. Cases 5 and Case 6 demonstrate the use of continuum infinite elements.
Far-field boundary conditions applied a significant distance from the region of interest have negligible influence on the response near the crack. In Case 1 through Case 4, the domain is extended well beyond the region of interest. The infinite half-space is treated using multiple techniques. However, the three-dimensional cases demonstrate the ABAQUS fracture mechanics capability, where the crack extension direction varies along a curved crack front. The geometry is axisymmetric and can be modeled as such. The crack is modeled as a seam since the crack surfaces in the unloaded state lie next to one another with no gap. This example includes six cases demonstrating different modeling approaches using ABAQUS/Standard. Submodeling and the use of infinite elements to simulate far-field boundaries are also demonstrated.ĪBAQUS modeling approaches and simulation techniques This example uses axisymmetric and three-dimensional models to demonstrate the ABAQUS fracture mechanics capability, where the crack extension direction varies along a curved crack front. The stress intensity factors,, relate to the energy release rate and measure the propensity for crack propagation. Together, the T-stress and the J-integral provide a two-parameter fracture model describing Mode I elastic-plastic crack-tip stresses and deformation in plane strain or three dimensions over a wide range of crack configurations and loadings. The T-stress represents stress parallel to the crack face. In practice, the calculated J-integral can be compared with a critical value for the material under consideration to predict fracture. The J-integral is a widely applied fracture mechanics parameter that relates to energy release associated with crack growth and is a measure of the deformation intensity at a crack tip.
ACCURATE 4 FULL CRACK HOW TO
It shows how to evaluate the propensity of the crack to propagate under static loading but does not cover the event that formed the crack. This example examines the fracture behavior of a conical crack, which may result from a small hard object impacting a large brittle body.
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