cgrow#

DataTables.cgrow(action='', par1='', par2='', par3='', **kwargs)#

Specifies crack-growth options in a fracture analysis.

Mechanical APDL Command: CGROW

Parameters:
actionstr

Specifies the action for defining or manipulating crack-growth data:

par1str

The description of the argument is missing in the Python function. Please, refer to the command documentation for further information.

par2str

The description of the argument is missing in the Python function. Please, refer to the command documentation for further information.

par3str

The description of the argument is missing in the Python function. Please, refer to the command documentation for further information.

Notes

When Action = NEW, the cgrow command initializes a crack-growth simulation set. Subsequent cgrow commands define the parameters necessary for the simulation.

For multiple cracks, issue multiple cgrow,NEW commands (and any subsequent cgrow commands necessary to define the parameters) for each crack.

If the analysis is restarted ( antype,,RESTART), the cgrow command must be re-issued.

If the save command is issued after any cgrow commands are issued, the cgrow commands are not saved to the database. Reissue the cgrow command(s) when the database is resumed.

For SMART -based crack-growth:

  • Action = CPATH has no effect.

  • Action = STOP affects both SMART-based static and fatigue crack-growth analyses.

  • When Action = CSFL with Option = CZM, the remeshing for cracks associated with this option is enforced at the end of the first load step and the first substep whether or not the crack grows at this moment. On original crack surfaces (defined via cint,SURF), INTER204 elements are initialized fully damaged, as they are used for crack-closure only and do not contribute bonding tractions on crack surfaces. The cohesive tractions on the new open crack surface are defined via the cohesive zone material model type ( tb,CZM) and cgrow,CSFL,CZM. This option can be combined with adpci to initialize a crack with cohesive effect.

For VCCT -based crack-growth:

  • Crack-growth element components must use the crack tip nodes as the starting nodes of the crack path.

  • Fracture criteria ( Action = FCOPTION) use energy-release rates calculated via VCCT technology ( cint,TYPE,VCCT). For information about the fracture criteria available, see Fracture Criteria tb, CGCR – Crack-Growth Fracture Criterion CGCR.

For XFEM -based crack-growth:

  • The crack specification originates via the xfenrich, xfdata, or xfcrkmesh command.

  • Action = CPATH, DTMIN, or DTMAX has no effect.

  • Action = STOP affects fatigue crack-growth analysis only.

Command Specifications#

Command Specification for Action= NEW

  • Par1 - Crack-growth data set ID (integer value).

Command Specification for Action= CID

  • Par1 - Contour-integral calculation ( cint ) ID for energy-release rates to be used in fracture criterion calculation.

Command Specification for Action= FCOPTION

  • Par1 - MTAB - Crack-growth fracture criterion used with the material data table (

tb, CGCR – Crack-Growth Fracture Criterion CGCR).

GTC - Defines the critical energy-release rate, a simple fracture criterion used for the VCCT method.

KIC - Defines the critical stress-intensity factor. Valid for the SMART method only.

JIC - Defines the critical J-integral. Valid for the SMART method only.

  • Par2 - For Par1 = MTAB: Material ID for the material data table.

    For I Par1 = GTC: Critical energy-release rate value.

    For Par1 = KIC: Critical stress-intensity factor value.

    For Par1 = JIC: Critical J-integral value.

  • Par3 - For Par1 = MTAB, KIC, or JIC: Specifies the fracture-parameter contour to use for SMART crack-growth evaluation. Default = 2.

Command Specification for Action= CSFL

  • Par1 - Crack-surface load options:

    • PRES - New crack-surface pressure load.

    • CZM - Entire crack-surface enhanced by INTER204 3D 16-node cohesive elements (generated automatically during the first remeshing around the associated crack). See CGROW_notes.

  • Par2 - When Par1 = PRES: (blank)

    When Par1 = CZM: A valid material ID (defined via tb,CZM,,,,BILI, tb,CZM,,,,CEXP, or tb,CZM,,,,CLIN [default]). If zero or an invalid value is specified, the program uses tb,CZM,,,,CLIN as the default cohesive model type and sets reasonable CZM parameters based on the solid elements around the crack fronts/surfaces. For more information, see Enhancing Crack Surfaces with Cohesive Zone Elements

  • Par3 - New crack-surface load value, or the name of a table for specifying tabular load values for crack- growth.

    The new crack-surface load is always assumed to be constant. If Par1 = PRES, Par3 specifies a constant pressure load.

    To specify a table ( dim ), enclose the table name within “%” characters (

    % tablename% ). Only one table can be specified for a crack-growth set, and time is the only

    primary variable supported.

    % tablename% ). Only one table can be specified for a crack-growth set, and time is the only

    primary variable supported.

Command Specification for Action= CPATH

  • Par1 - Interface element component for crack path ( VCCT method only). (Component name must be 32 characters or less.)

Command Specification for Action= DTIME

  • Par1 - Initial time step when crack-growth is detected.

Command Specification for Action= DTMIN

  • Par1 - Minimum time step allowed when crack-growth is detected.

Command Specification for Action= DTMAX

  • Par1 - Maximum time step allowed when crack-growth is detected.

Command Specification for Action= FCRAT

  • Par1 - Fracture criterion ratio (f:sub:c, where f:sub:c is generally around 1). The recommended ratio is 0.95 to 1.05. The default is 1.00.

Command Specification for Action= STOP

  • Par1 - CEMX - Stops the analysis when the crack extension for any crack-front node reaches

the maximum value

(specified via Par2 ).

FBOU - Stops the analysis when the crack extension reaches the free boundary. Valid only for SMART crack-growth analysis.

KMAX - Stops the analysis when the maximum equivalent stress-intensity factor exceeds the specified limit ( Par2 ). Valid only for SMART crack-growth analysis.

  • Par2 - When Par1 = CEMX, the value of maximum crack extension allowed.

    When Par1 = KMAX, the value of the maximum equivalent stress-intensity factor allowed.

Command Specification for Action= METHOD

  • Par1, Par2 - VCCT - Use `VCCT

<https://ansyshelp.ansys.com/Views/Secured/corp/v232/en/ans_frac/Hlp_G_STR_VCCT.html#vcctsimassum>`_ to grow the crack (default).

XFEM - Use XFEM to grow the crack.

SMART - Use SMART to grow the crack.

  • Par2 - REME - Remeshing-based SMART crack-growth method (the default and only option). Valid only when Par1 = SMART.

Command Specification for Action= FCG

  • Par1 - METH - Fatigue crack-growth method.

    DAMX - Maximum crack-growth increment.

    DAMN - Minimum crack-growth increment.

    SRAT - Stress ratio.

    DKTH - Threshold value of equivalent stress-intensity-factor range (SIFS).

    DN - Incremental number of cycles.

  • Par2 - Method - LC or CBC method CBCmethod. Valid only when Par1 = METH.

    VALUE - Value for the specified Par1. Valid only when Par1 = DAMX, DAMN, SRAT, DKTH, or DN.

    • For Par1 = SRAT or DKTH, Par2 can be a constant or table. To specify a table ( dim ), enclose the table name within “%” characters (tablename). Only one table can be specified for a crack-growth set, and time is the only primary variable supported.

  • Par3 - Valid only for SMART crack-growth analysis when Par1 = DKTH.

    MIN or MAX or AVER or blank (default) - The minimum, maximum, or average stress-intensity-factor range (ΔK), respectively. The program calculates the range over the entire crack front, then uses the result to evaluate the threshold criterion. The entire crack is arrested if the specified minimum, maximum, or average ΔK is below the threshold ( Par2 ). Partial crack-growth does not occur.

    If Par3 is unspecified (default), the program evaluates threshold criterion at each crack-front node individually and ensures that the crack is arrested locally at any node where ΔK is below the threshold ( Par2 ). If some nodes have ΔK less than the threshold and others have ΔK greater than the threshold, partial crack-growth occurs at the crack front.

    **Example: Using

    CGROW,FCG,DKTH, Par2, Par3

    **

    If Par3 = MIN, the program selects the minimum ΔK from the ΔK values calculated at all crack- front nodes for the corresponding crack ID. If the minimum ΔK does not exceed the threshold ( Par2 ), there is no crack extension at the entire crack front.

Command Specification for Action= SOPT

  • Par1 - SCN - Use a single number of cycles for all cracks in a multicrack analysis (even if each crack has separate loading) (default).

    MCN - Allow a separate cycle count for each crack in a multicrack analysis (available only if each crack has separate loading).

Command Specification for Action= RMCONT

Valid in a SMART crack-growth analysis only.

  • Par1 - COARSE - Controls mesh-coarsening.

    ESIZE - Controls element sizing and crack-increment size.

    CMULT - Controls the crack-growth increment multiplier.

  • Par2 - For Par1 = COARSE:

    • CONS - Remeshing occurs with conservative mesh-coarsening (default).

    • MODE - Remeshing occurs with moderate mesh-coarsening.

    • AGGR - Remeshing occurs with aggressive mesh-coarsening.

    For Par1 = ESIZE:

    • Crack-front reference element-size value, or the table name for specifying tabular element size values as a function of solution time.

    For Par1 = CMULT:

    • Crack-front element-size multiplier function :

    • TIME - Controls the crack-growth increment multiplier via the beginning and end of the solution time.

    • CEMX - Controls the crack-growth increment multiplier via the beginning and end of the accumulated maximum crack extension.

    • RMNU - Controls the crack-growth increment multiplier via the beginning and end of the number of remeshing steps.

    • TABLE - The name of the table for controlling the crack-growth increment multiplier.

  • Par3 - Par5 - For Par1 = ESIZE and Par2 = VALUE or tablename and Par3 =

COMP:

  • Par4 = Name of the node or element component (≤ 32 characters).

For Par1 = ESIZE and Par2 = VALUE or tablename and Par3 = NODE:

  • Par4 = Node ID.

For Par1 = ESIZE and Par2 = VALUE or tablename and Par3 = ELEM:

  • Par4 = Element ID.

For Par1 = CMULT and Par2 = TIME:

  • Par3 = VALUE - Maximum value of the crack-growth multiplier value.

  • Par4 = VALUE - Time at the beginning of the crack-increment control function.

  • Par5 = VALUE - Time at the end of the crack-increment control function.

For Par1 = CMULT and Par2 = CEMX:

  • Par3 = VALUE - Maximum value of the crack-growth multiplier value.

  • Par4 = VALUE - Accumulated maximum crack extension at the beginning of the crack-increment control function.

  • Par5 = VALUE - Accumulated maximum crack extension at the end of the crack-increment control function.

For Par1 = CMULT and Par2 = RMNU:

  • Par3 = VALUE - Maximum value of the crack-growth multiplier value.

  • Par4 = VALUE - Remeshing number at the beginning of the crack-increment control function.

  • Par5 = VALUE - Remeshing number at the end of the crack-increment control function.

For Par1 = CMULT and Par2 = TABLE:

  • Par3 = tablename - Controls the crack-growth increment multiplier via the tabular data in the specified table.

  • To specify a table ( dim ), enclose the table name tablename within % characters. You can specify one table per crack-growth set, and time is the only valid variable.

Command Specification for Action= NPLOAD

Valid in a SMART fatigue crack-growth analysis using nonproportional loading.

  • Par1 - METHOD - Specifies the nonproportional solution method.

    DIRECTION - Specifies the nonproportional crack-growth-direction method.

  • Par2 - For Par1 = METHOD:

    • DKEF - Specifies the effective stress-intensity-factor range method.

    • DKMO - Specifies the stress-intensity-factor range method based on mode separation.

    • TKEF - Specifies the total effective stress-intensity-factor method.

    • TKMO - Specifies the total stress-intensity-factor method based on mode separation.

    For Par1 = DIRECTION:

    • KMAX - Specifies the maximum-load method for the crack-growth direction.

    • KMIN - Specifies the minimum-load method for the crack-growth direction.

    • KLOC - Specifies the local kink-tip stress-intensity-factor method.

  • Par3 - For Par2 = KLOC:

    • w - Parameter-fitting value between 0 and 1. Default = 0.5.