Mechanical APDL Structural Analysis Guide

The VCCT method for energy-release rat e calculation supports the following material behaviors:

• Linear isotropic elasticity


• Orthotropic elasticity


• Anisotropic elasticity

11.3.2.2. Process for Calculating the Energy-Release Rat e

The CINT command's VCCT option initiates the energy-release rat e calculation.

Similar to the J-integral calculation,CINT specifies the parameters necessary for the calculation.

For CINT element-type and material-behavior support, see Element Selection and Material Behavi-
or (p. 352).

Following is the general process for calculating the energy-release rate:

11.3.2.2.1. Step 1: Initiate a New Energy-Release Rat e Calculation

11.3.2.2.2. Step 2: Define Crack Information

11.3.2.2.3. Step 3: Define a Crack Symmetry Condition

11.3.2.2.4. Step 4: Specify Output Controls

11.3.2.2.1. Step 1: Initiate a New Energy-Release Rate Calculation

Issue the CINT command twice, as shown:

CINT,NEW,n

CINT,TYPE,VCCT

where n is the identifier for this energy-release rat e calculation (for example, 1).

11.3.2.2.2. Step 2: Define Crack Information

Similar to the J-integral calculation, the crack-tip node component and the crack-extension direction
are both necessary for the energy-release rat e calculation.

VCCT requires the finite element mesh to be in the crack-extension direction. To ensure the accuracy
of the energy-release rat e calculation, it is crucial that you correctly define the crack extension. How
you do so depends upon whether the crack plane is flat or not:

11.3.2.2.2.1. Specifying Crack Information When the Crack Plane Is Flat

11.3.2.2.2.2. Specifying Crack Information When the Crack Plane Is Not Flat

11.3.2.2.2.1. Specifying Crack Information When the Crack Plane Is Flat

This approach applies to both 2-D crack geometry and 3-D flat crack surfaces. It offers a simple way to
define a 3-D energy-release rat e calculation, as you need only define the crack-tip (front) node component
and the normal of the crack plane.

2-D Flat Crack Geometry

For 2-D crack geometry, define a crack-tip node component (usually a node located at the crack tip).

You can also define a group of nodes around the crack tip, including the node at the crack tip. The

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Numerical Evaluation of Fracture Mechanics Parameters