*FATIGUE

Define a fatigue crack growth analysis in bulk brittle materials and in brittle material interfaces.

This option is used to predict delamination/debonding growth at the brittle material interfaces in laminated composites and to predict crack growth in bulk brittle materials under cyclic fatigue loading.

This page discusses:

See Also
*TIME POINTS
In Other Guides
Linear Elastic Fatigue Crack Growth Analysis

ProductsAbaqus/Standard

TypeHistory data

LevelStep

Optional parameters

CETOL

Set this parameter equal to the maximum difference in the creep strain increment calculated from the creep strain rates based on conditions at the beginning and on conditions at the end of the increment, thus controlling the time integration accuracy of the creep integration.

This parameter can be used in conjunction with the TIME POINTS option. In this case Abaqus/Standard ensures that the response is also evaluated at each time point specified on the TIME POINTS option.

If both this parameter and the DELTMX parameter are omitted, fixed time stepping will be used, with a constant time increment equal to the initial time increment or by following precisely the time points specified on the TIME POINTS option.

DELTMX
Set this parameter equal to the maximum temperature change to be allowed in an increment during a fatigue crack growth analysis. Abaqus/Standard restricts the time increment to ensure that this value is not exceeded at any node during any increment of the step.
DIRECT
This parameter selects direct user control of the incrementation through the step. If this parameter is used, constant increments of the size defined by the first item on the data line are used. If this parameter is omitted, Abaqus/Standard will choose the increments (after trying the user's initial time increment for the first attempt at the first increment).
TIME POINTS
Set this parameter equal to the name of the TIME POINTS option that defines the time points at which the response of the structure will be evaluated.
TYPE
Set TYPE=CONSTANT AMPLITUDE (default) to use the classical incremental method for each cycle.

Set TYPE=SIMPLIFIED to use a constant load to simplify the fatigue loading. At least two increments are required for each single loading cycle in this case.

Data lines to define fatigue crack growth analysis

First line
  1. Initial time increment. If this entry is omitted, a default value of 0.1 times the single loading cycle period is assumed.
  2. Time of a single loading cycle.
  3. Minimum time increment allowed.
  4. Maximum time increment allowed.
Second line

  1. Minimum increment in number of cycles over which the damage is extrapolated forward. It must be greater than 0, and the default is 100.

  2. Maximum increment in number of cycles over which the damage is extrapolated forward. It must be greater than 0, and the default is 1000.

  3. Total number of cycles allowed in a step. If this entry is zero or not specified, the default value is equal to one plus half of the maximum increment in number of cycles over which the damage is extrapolated.

  4. Not used.

  5. Cycle increment–based tolerance for the least number of cycles to fracture an element. The damage-based tolerance takes precedence over the cycle increment–based tolerance if both are specified. If neither tolerance is specified, a damage-based tolerance with a default value of 0.25 is used.

  6. Damage-based tolerance for the least number of cycles to fracture an element. The damage-based tolerance takes precedence over the cycle increment–based tolerance if both are specified. If neither tolerance is specified, a damage-based tolerance with a default value of 0.25 is used.