Mechanical APDL Structural Analysis Guide

The modified B-K criterion is intended for composite interfacial fracture to account for distinct Mode II
and Mode III critical energy-release rates, and is suitable for 3-D mixed-mode fracture simulation.

Example 12.5: Modified B-K Criterion Input

g1c=10.0

g2c=20.0

g3c=25.0

h=2

TB,CGCR,1,,,MBK

TBDATA,1,g1c,g2c,g3c,h

12.1.3.6. Power Law Fracture Criterion

The power law [ 10 ] option assumes that the fracture criterion is a power function of the Mode I (GI),
Mode II (GII), and Mode III ((GIII) energy-release rates, expressed as:

I

I

C

n

II

II

C

n

III

III

C

n

=

















+

















+

















1 2 3

where

, 



, and 


are Mode I, Mode II, and Mode III critical energy-release rates, respectively,
and n 1 , n 2 , and n 3 are power exponents and are also constants. All six 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

Critical Mode III energy-release rate, 



> 0

C3





n 1 C4 n 1 > 0

n 2 C5 n 2 > 0

n 3 C6 n 3 > 0

The three critical energy-release rat es cannot all be zero. If a constant is set to zero, the corresponding
term is ignored.

When power exponents n 1 , n 2 , and n 3 are set to 1, the power law criterion is reduced to the linear

fracture criterion.

The power law 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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Interface Delamination and Failure Simulation