ABAQUS Keywords Reference Manual  

*FRACTURE CRITERION
Specify crack propagation criteria.

This option is used to specify the criterion for crack propagation along initially partially bonded surfaces. It must appear immediately following the *DEBOND option.

Product: ABAQUS/Standard  

Type: History data

Level: Step  

References:

Required parameters:

DISTANCE

This parameter is required only if TYPE=COD or TYPE=CRITICAL STRESS is used.

If TYPE=CRITICAL STRESS, set this parameter equal to the distance along the potential crack surface ahead of the crack tip at which the critical stress criterion is evaluated.

If TYPE=COD, set this parameter equal to the distance behind the crack tip along the slave surface at which the crack opening displacement is measured.

NSET

This parameter is required only if TYPE=CRACK LENGTH. Set this parameter equal to the name of the node set containing the nodes that are used to define the reference point.

TYPE

Set TYPE=CRITICAL STRESS to use the critical stress criterion at a distance ahead of the crack tip as the crack propagation criterion.

Set TYPE=COD to use the critical value of the crack opening displacement at a distance behind the crack tip as the crack propagation criterion.

Set TYPE=CRACK LENGTH to specify the crack length as a function of time.

Optional parameters:

DEPENDENCIES

This parameter is relevant only for TYPE=COD or TYPE=CRITICAL STRESS. Set this parameter equal to the number of field variable dependencies included in the data lines. If this parameter is omitted, it is assumed that the data are constant or depend only on temperature. See “Specifying field variable dependence” in “Material data definition,” Section 9.1.2 of the ABAQUS Analysis User's Manual, for more information.

SYMMETRY

Include this parameter to compare the opening between the slave surface and the symmetry plane to half the COD value specified. The SYMMETRY parameter is relevant only for TYPE=COD when the user is using symmetry conditions to model the problem. In this case the NORMAL parameter must be specified on the *INITIAL CONDITIONS option.

TOLERANCE

Set this parameter equal to the tolerance within which the crack propagation criterion must be satisfied. The default is TOLERANCE=0.1.

Data lines to define the critical stress criterion (TYPE=CRITICAL STRESS): 

First line:

  1. Normal failure stress, .

  2. Shear failure stress, .

  3. Shear failure stress, . (Not applicable in two dimensions.)

  4. Temperature.

  5. First field variable.

  6. Second field variable.

  7. Etc., up to four field variables.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than four):

  1. Fifth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the critical stress criterion as a function of temperature and/or field variables.

Data lines to define the crack opening displacement criterion (TYPE=COD): 

First line:

  1. Critical crack opening displacement, .

  2. Cumulative crack length.

  3. Temperature.

  4. First field variable.

  5. Second field variable.

  6. Etc., up to five field variables.

Subsequent lines (only needed if the DEPENDENCIES parameter has a value greater than five):

  1. Sixth field variable.

  2. Etc., up to eight field variables per line.

Repeat this set of data lines as often as necessary to define the crack opening displacement criterion as a function of temperature and/or field variables.

Data lines to define the crack length versus time criterion (TYPE=CRACK LENGTH): 

First line:

  1. Total time (not step time).

  2. Crack length, , from the reference point.

  3. Etc., up to four time/length pairs per line. Crack length must be given as an increasing function of time.

Repeat this data line as often as necessary to define the crack length as a function of time.