Mechanical APDL Structural Analysis Guide

For Mode I fracture, the fracture criterion reduces to:

I

I

= C

The critical energy-release rat e option is the simplest fracture criterion and is suitable for general 2-D
and 3-D crack growth simulation.

Example 12.1: Critical Energy Release Rate Input

gtcval=10.0

CGROW,FCOPTION,GTC,gtcval

12.1.3.2. Linear Fracture Criterion

The linear option assumes that the fracture criterion is a linear function of the Mode I (GI), Mode II (GII),
and Mode III ((GIII) energy-release rates, expressed as:

= + + 

where 



, 



, and 


are the Mode I, Mode II, and Mode III critical energy-release rates, respectively.
The three values are input via the TBDATA command, as follows:

TBDATA Comments

Input

Constant

Critical Mode I energy-release rate, 

>= 0

C1

Critical Mode II energy-release rate,^

>= 0

C2





Critical Mode III energy-release rate, 



>= 0

C3





Example 12.2: Linear Criterion Input

g1c=10.0

g2c=20.0

g3c=25.0

TB,CGCR,1,,,LINEAR

TBDATA,1,g1c,g2c,g3c

The three constants cannot all be zero. If a constant is set to zero, the corresponding term is ignored.

When all three critical energy-release rat es are equal, the linear fracture criterion reduces to the critical
energy-release rat e criterion.

The linear fracture criterion is suitable for 3-D mixed-mode fracture simulation where distinct Mode I,
Mode II, and Mode III critical energy-release rat es exist.

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VCCT-Based Crack Growth Simulation