Mechanical APDL Structural Analysis Guide

For a simple fracture criterion such as the critical energy-release rate, you can specify it by issuing the
CGROW,FCOPTION,GC,value command, where value is the critical energy-release rate.

For a more complex fracture criterion, you can specify the fracture criteria via a material data table. Issue
the CGROW,FCOPTION,MTAB,matid command, where matid is the material ID for the material table.
Several fracture criterion options are available (such as linear, bilinear, B-K, modified B-K, Power Law,
and user-defined).

For more information, see the TB,CGCR command and Fracture Criteria (p. 386).

For each crack growth set, you can specify only one fracture criterion, and one element component for
crack growth. You can define multicrack growth sets with different cracks and fracture criteria. Multiple
cracks can grow simultaneously and independently from each other. Cracks can merge to a single crack
when they are on the same interface, as shown in the following figure:

Figure 12.2: Crack Growth and Merging

You can also define the same crack with different fracture criteria in a separat e crack growth set.The
cracks can grow based on different criteria (according to which criterion is met), and are independent
from each other. This technique is useful for comparing facture mechanisms.

12.1.1.3.4. Step 3d: Specify Solution Controls for Crack Growth

Issue the CGROW command to specify solution controls, as follows:

To specify this solution con- Issue this CGROW command:

trol...

Fracture criterion ratio (fc) CGROW,FCRAT,value,

where value is the ratio

Initial time step when crack CGROW,DTIME,value,

growth initiates where value is initial time step

To avoid over-predicting the load-car-

rying capacity, specify a small initial

time step.

Minimum time step for sub- CGROW,DTMIN,value,

sequent crack growth where value is the minimum time step

size

Maximum time step for sub- CGROW,DTMAX,value,

sequent crack growth where value is the maximum time step

size

Maximum crack ext ension al- CGROW,STOP,CEMX,value,

lowed at any crack front nodes

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Interface Delamination and Failure Simulation