Mechanical APDL Structural Analysis Guide

irregular behavior of the stress-intensity factor distribution along crack front. The program automatically
calculate the local coordinate systems based on the input crack front nodes and the normal of the crack
surface or ext ension directions; however, because there may be not enough information to determine
a set of consistent coordinate systems, ANSYS, Inc. recommends using the CINT command's CTNC option
to define a crack-face node to help identify the coordinate systems, or use the NORM option with the
CENC option to define the coordinate systems.

11.3.3.1.2.3. Step 3: Specify the Number of Contours

The interaction integral, and thus the stress-intensity factors, have the same contour-independent be-
havior as the J-Integral. You can specify the number of contours for the interaction integral evaluation,
as follows:

CINT,NCON,n

where n is the number of contours.

For 3-D crack geometry, every node along the crack front has the same number of contours.

Example

CINT,NEW,1

CINT,TYPE,SIFS

CINT,CTNC,CRACK_FRONT_NODE_SET,NODE

CINT,NCON,6

11.3.3.1.2.4. Step 4: Define a Crack Symmetry Condition

In general, there is no crack symmetry condition for a mixed-mode crack. When a crack symmetry
condition is defined, however, stress-intensity factor KII and KIII are both set to zero. The calculated in-
teraction integral is timed by a factor of two and is used to calculate the stress-intensity factor KI.

The command to define a symmetric condition is as follows:

CINT,SYMM,ON

Example

CINT,NEW,1

CINT,TYPE,SIFS

CINT,SYMM,ON! crack #1 is a symmetrical crack

11.3.3.1.2.5. Step 5: Specify Output Controls

Similar to the J-Integral calculation, Mechanical APDL calculates the stress-intensity factors during the
solution phase of the analysis and stores it to the results file for postprocessing. Stress-intensity factors
output uses all the defaults from the OUTRES command. The command OUTRES,ALL includes CINT
command results. However, you can issue an OUTRES,CINT command to control the specific output for
stress-intensity factors results only.

Example

CINT,NEW,1

CINT,TYPE,SIFS

CINT,CTNC,CRACK_TIP_NODE_CM

CINT,SYMM,ON

CINT,NCON,5

OUTRES,CINT,10! output CINT results every 10 substeps

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

Fracture Mechanics