CGROW

CGROW, Action, Par1, Par2, Par3, Par4
Specifies crack-growth options in a fracture analysis.

Valid Products: Pro | Premium | Enterprise | PrepPost | Solver | AS add-on

Action

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

NEW

 — 

Initiate a new set of crack-growth simulation data (default).

CID

 — 

Specify the crack-calculation (CINT) ID for energy-release rates to be used in the fracture criterion calculation.

CGID

 — 

Activate an existing crack-growth ID to modify its crack-growth settings via subsequent CGROW commands.

FCOPTION

 — 

Specify the fracture criterion for crack-growth/delamination.

CSFL

 — 

Specify a crack-surface load for crack-growth.

CPATH

 — 

Specify the element component for crack-growth.

DTIME

 — 

Specify the initial time step for crack-growth.

DTMIN

 — 

Specify the minimum time step for crack-growth.

DTMAX

 — 

Specify the maximum time step for crack-growth.

FCRAT

 — 

Fracture criterion ratio (fc).

STOP

 — 

Stop the analysis when the specified criterion (Par1) is reached.

METHOD

 — 

Define the method of crack propagation.

FCG

 — 

Specify fatigue crack-growth.

SOPT

 — 

Specify crack-growth solution options.

RMCONT

 — 

Specify remeshing control options for mesh coarsening.

NPLOAD

 — 

Specify nonproportional loading control options for fatigue crack-growth.

Command Specification for Action = NEW

CGROW, NEW, Par1

Par1 –

Crack-growth data set ID (integer value).

Command Specification for Action = CID

CGROW, CID, Par1

Par1 –

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

Command Specification for Action = CGID

CGROW, CGID, Par1

Par1 –

Crack-growth data set ID (integer value).

Command Specification for Action = FCOPTION

CGROW, FCOPTION, Par1, Par2, Par3

Par1 –

MTAB – Crack-growth fracture criterion used with the material data table (TB,CGCR).

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

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

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

Par2 –

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

For 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: Specify the fracture-parameter contour to use for SMART crack-growth evaluation. Default = 2.

Command Specification for Action = CSFL

CGROW, CSFL, Par1, Par2, Par3

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 "Notes".
Par2 –

When Par1 = PRES:

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 in the Fracture Analysis Guide.
Par3 –

When Par1 = PRES:

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.

When Par1 = CZM:

A valid local coordinate system (LCS) ID (LOCAL).
If zero or an invalid value is specified, the program creates an internal LCS and assigns it to the ESYS attributes of CZM elements inserted on crack surfaces. This behavior applies only when the material ID (MAT_ID) for Par3 is associated with TB,CZM when TBOPT = FRIC or REXP. For more information, see Enhancing Crack Surfaces with Cohesive Zone Elements in the Fracture Analysis Guide.

Command Specification for Action = CPATH

CGROW, CPATH, Par1

Par1 –

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

Command Specification for Action = DTIME

CGROW, DTIME, Par1

Par1 –

Initial time step when crack-growth is detected.

Command Specification for Action = DTMIN

CGROW, DTMIN, Par1

Par1 –

Minimum time step allowed when crack-growth is detected.

Command Specification for Action = DTMAX

CGROW, DTMAX, Par1

Par1 –

Maximum time step allowed when crack-growth is detected.

Command Specification for Action = FCRAT

CGROW, FCRAT, Par1

Par1 –

Fracture criterion ratio (fc, where fc is generally around 1). The recommended ratio is 0.95 to 1.05. The default is 1.00.

Command Specification for Action = STOP

CGROW, STOP, Par1, Par2

Par1 –

CEMX – Stop the analysis when the crack extension for any crack-front node reaches the maximum value (Par2).

CNMX – Stop the analysis when the maximum number of fatigue cycles exceeds the specified limit (Par2). Valid only for SMART crack-growth analysis.

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

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

DN – Stop the analysis when the fatigue-cycle increment number is less than or equal to the specified limit (Par2). Valid only for SMART crack-growth analysis.

Par2 –

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

When Par1 = CNMX, the maximum number of fatigue cycles allowed.

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

When Par1 = DN, the minimum limit for fatigue-cycle increment. Default = 0.

Command Specification for Action = METHOD

CGROW, METHOD, Par1

Par1, Par2 –

VCCT – Use VCCT 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

CGROW, FCG, Par1,Par2,Par3

Par1 –

METH – Fatigue crack-growth method.

DAMX – Maximum crack-growth increment (XFEM method only).

DAMN – Minimum crack-growth increment (XFEM method only).

SRAT – Stress ratio.

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

DN – Incremental number of cycles.

Par2 –

Method – LC or CBC method. 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 2: 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

CGROW,SOPT,Par1,Par2,Par3,Par4

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).

MXAN – Specify the maximum limit of the crack-growth kinking angle.

MNAN – Specify the cut-off value for the minimum crack-growth kinking angle.

DAMX – Specify the maximum limit of crack-growth increment.

DAMN – Specify the minimum limit of crack-growth increment.

SPLO – Specify spectrum fatigue loading.

KEQV – Specify the method for the equivalent stress-intensity factor calculation.

KANG – Specify the method for the kink angle calculation.

Par2 –

For Par1 = MXAN:

Value (in degrees) of the maximum limit of the crack-growth kinking angle. If CGROW,SOPT,MXAN,Par2 is not issued (or Par2 is unspecified), the program uses a default kinking-angle limit of 20 degrees. Par2 = 0 forces mode-I crack propagation.

For Par1 = MNAN:

Cut-off value (in degrees) for the minimum crack-growth kinking angle. Default = 1.

For Par1 = DAMX:

Value to determine the maximum crack-growth increment. Default: damax = 1.5 * ESIZE, where ESIZE is the reference-element size at the crack-front at any substep.

For Par1 = DAMN:

Value to determine the minimum crack-growth increment. Default: damin = 0.

For Par1 = SPLO:

WEIG – Define the damage weight average method for the crack-growth direction (default).
DMAX – Define the dominative load point (maximum damage) method for the crack-growth direction.

For Par1 = KEQV:

MTS – Maximum tangential stress criterion (default).
RICHARD – Richard approximation function.
POOK – Pook criterion.
EMPS – Empirical function based on square root of sum of squares.

For Par1 = KANG:

MTS – Maximum tangential stress criterion (default).
RICHARD – Richard approximation function.
Par3 –

For Par1 = DAMX or DAMN:

ABSO – Indicate that Par2 is the absolute value (default). The corresponding limit (damax or damin) is Par2.
MULT – Indicate that Par2 is a multiplier of the reference-element size (ESIZE) at the crack-front at any substep. The corresponding limit (damax or damin) is Par2 * ESIZE.

For information about controlling the element size (ESIZE) at the crack-front, see CGROW,RMCONT,ESIZE and CGROW,RMCONT,CMULT.

For Par1 = KEQV and Par2 = RICHARD or EMPS:

– multiplicative factor in term in the corresponding function for equivalent SIF.

For Par1 = KANG and Par2 = RICHARD:

– coefficient of first order term in the Richard function for the kink angle.
Par4 –

For Par1 = DAMN:

0 – Set the crack increments less than damin (specified via Par2) as = damin. It is the default option if Par2 > 0.
1 – Set the crack increments less than damin as = 0.

If Par2 = 0, the program sets any crack increment less than two percent of the reference-element size at the crack-front as = 0.

For Par1 = KEQV and Par2 = RICHARD or EMPS:

– multiplicative factor in term in the corresponding function for the equivalent SIF.

For Par1 = KANG and Par2 = RICHARD:

– coefficient of second order term in the Richard function for the kink angle.

Command Specification for Action = RMCONT

CGROW,RMCONT,Par1,Par2,Par3,Par4,Par5

Valid in a SMART crack-growth analysis only.

Par1 –

COARSE – Control mesh-coarsening.

ESIZE – Control element sizing and crack-increment size.

CMULT – Control 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 – Control the crack-growth increment multiplier via the beginning and end of the solution time.
CEMX – Control the crack-growth increment multiplier via the beginning and end of the accumulated maximum crack extension.
RMNU – Control 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% – Control 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

CGROW,NPLOAD,Par1,Par2,Par3

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

Par1 –

METHOD – Specify the nonproportional solution method.

DIRECTION – Specify the nonproportional crack-growth-direction method.

Par2 –

For Par1 = METHOD:

DKEF – Specify the effective stress-intensity-factor range method.
DKMO – Specify the stress-intensity-factor range method based on mode separation.
TKEF – Specify the total effective stress-intensity-factor method.
TKMO – Specify the total stress-intensity-factor method based on mode separation.

For Par1 = DIRECTION:

KMAX – Specify the maximum-load method for the crack-growth direction.
KMIN – Specify the minimum-load method for the crack-growth direction.
KLOC – Specify the local kink-tip stress-intensity-factor method.
Par3 –

For Par2 = KLOC:

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

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.

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 in the Fracture Analysis Guide or TB,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.

Menu Paths

This command cannot be accessed from a menu.