12.1.3.3. Bilinear Fracture Criterion

The bilinear fracture option [ 8 ] assumes that the fracture criterion is a linear function of the Mode I (GI)
and Mode II (GII) energy-release rates, expressed as:

I II

I

C

II I

II

C

II

I

I

C

II

C

I

C

= II

−

−















<

+

+

ξ

ζ

ζ

ξ

ζ

1

CC

II

I

I

C

II

C

I

C

II

> C

+

+

1

ζ

ξ

where

and 


are the Mode I and Mode II critical energy-release rates, respectively, and ξ and ζ
are the two material constants. All four values can be defined as a function of temperature and 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

ξ C3 ξ > 0

ζ C4 ζ > 0

Example 12.3: Bilinear Criterion Input

g1c=10.0

g2c=20.0

x=2

y=2

TB,CGCR,1,,,BILINEAR

TBDATA,1,g1c,g2c,x,y

The bilinear fracture criterion is suitable for 2-D mixed-mode fracture simulation.

12.1.3.4. B-K Fracture Criterion

The B-K [ 7 ] option is expressed as:

T

(^)
T

+( − )
 +





η
where 

and 

are the Mode I and Mode II critical energy-release rates, respectively, and η is the
material constant. All three values can be defined as a function of temperature and are input via the
TBDATA command, as follows:
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Interface Delamination and Failure Simulation