Within the Pre-Mesh Crack object, the Node sets created previously are allocated to the crack front, and the crack top and bottom faces. The crack coordinate system is referenced. The number of solution contours is set to 5. The Fracture Mechanics approach avoids the stress singularities at the crack tip in the analysis. The Pre-Meshed crack object is selected, the option to carry out a Static Fatigue analysis is chosen and the Critical Fracture Toughness is defined.
The Stress Intensity Factor method is selected in this case. This calculation is done along the distributed crack front, and the distribution of Stress Intensity Factor will control the adapting crack front shape. The Failure Criteria can also be set to the J-Integral method. The main fracture mechanism in this model is the crack tensile opening Mode 1, which calculates K I. These values are secondary for this configuration but may become important for a crack that changes direction significantly with a resulting shear stress environment.
I have also included a crack extension probe to monitor the crack growth. Each of these probes will produce an XY plot. I have constrained the bottom surface of the test piece and applied a vertical force of 1. The initial crack length is 6.
A manual calculation gives a value for KI of 6. This is below the Critical Kc of 1. The component will not fracture under this loading. The main objective is to check the value and distribution of K I.
After launching the analysis, the distribution of K I along the crack front is shown in Fig. The manual calculation referenced is for an assumed infinitely deep plane strain section and is a one-dimensional 1D approximation. The value matches the finite element analysis FEA distribution well. The edge effect can be seen in the 3D model. There are five curves shown in Fig. These represent the five contours requested in the Pre-Mesh Crack object.
They are used to check for convergence of the KI value. The first curve is from a contour close to the crack tip; the other curves represent contours at increasing distances.
The curves converge quickly, showing the mesh is adequate. This is greater than K c and results in a static fracture. Running the model with 40 Substeps results in a crack extension of The maximum stress contours are adjusted at each step. The location to sample along the crack front can be selected, and I have used the midpoint of the crack front. No geometric nonlinearity allowed—so the crack length here is limited realistically unless we use a displacement control.
The eccentricity created by the crack would result in very large bending stresses in the residual material, as the crack runs out, with a resulting complex failure mechanism. A crack extension limit can be defined to prevent an unrealistically long crack. This requires additional material data definitions for the Paris Law. The Paris Law is defined by:. The additional data required are the coefficient and exponent.
The units of the coefficient material data are tricky as they embody the exponent m in the conversion. I will be writing about non-intuitive units in a future article! Create new account Request new password. Navigation Search iMechanica. Writing a paper Writing a proposal in situ Mechanics tensor tensor and its invariants. You are here Home. Thanks I cant use any other software, only Ansys. Thank you. I used for the first time the CINT command with ansys, and I get strange results: negative values very different values for 2 adjacent nodes on the crack front non converging values values fluctuating from 1 contour to another, going up and down Also, i don't know what are the units of the J integral I am using SI units, dimensions in mm.
Anybody have some information for me? Fracture Mechanics Forum. Free Tags:. What is the easiest way to define a cracked area, and crack front and then mesh it How can i merge together a cracked area and an unmeshed area? Olivares Forums:. The appropriate license for your computer is created in the form of a file called license. After installation, click Next and wait for the License Wizard window to appear; Select the first and default option and click Continue.
Then give the license. In the second method, start installing the program and do not install the lead license. After installation, copy and replace the two cracked files in the following location:.
If you are installing software in a location other than the default drive, you must edit its address in the ansyslmd. Table of Contents.
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