CNCHECK
CNCHECK, Option, RID1, RID2, RINC, PairType, TRlevel
Provides and/or adjusts the initial status of contact pairs.
MP ME ST PR PRN <> <> FL EM EH <> PP <> EME MFS
Option

Option to be performed:

DETAIL — 

List all contact pair properties (default).

SUMMARY — 

List only the open/closed status for each contact pair.

POST — 

Execute a partial solution to write the initial contact configuration to a results file, Jobname.RCN.

ADJUST — 

Physically move contact nodes to target to close gap or reduce penetration.

RESET — 

Reset target element and contact element key options and real constants to their default values.

AUTO — 

Automatically sets certain real constants and key options to recommended values or settings in order to achieve better convergence based on overall contact pair behaviors.

TRIM — 

Trim contact pair (remove certain contact and target elements).

UNSE — 

Unselect certain contact and target elements.

RID1, RID2, RINC

The range of real constant pair ID's for which Option will be performed. If RID2 is not specified, it defaults to RID1. If no value is specified, all contact pairs in the selected set of elements are considered.

PairType

Type of contact pairs to be trimmed/unselected/auto-set (used only when Option = TRIM, UNSE, or AUTO):

ANY — 

All types (default).

MPC — 

MPC-based contact pairs (KEYOPT(2) = 2).

BOND — 

Bonded contact pairs (KEYOPT(12) = 3, 5, 6).

NOSP — 

No separation contact pairs (KEYOPT(12) = 2, 4).

INAC — 

Inactive contact pairs (symmetric contact pairs for MPC contact or KEYOPT(8) = 2).

TRlevel

Trimming level (used only when Option = TRIM or UNSE):

(blank) — 

Normal trimming (default): remove/unselect contact and target elements which are in far-field.

AGGRE — 

Aggressive trimming: remove/unselect contact and target elements which are in far-field, and certain elements in near-field.

Notes

The CNCHECK command provides information for surface-to-surface, node-to-surface, and line-to-line contact pairs (element types TARGE169, TARGE170, CONTA171, CONTA172, CONTA173, CONTA174, CONTA175, CONTA176, CONTA177). All contact and target elements of interest, along with the solid elements and nodes attached to them, must be selected for the command to function properly.

CNCHECK is available in both the PREP7 and SOLUTION processors, but only before the first solve operation (that is, only before the first load step or the first substep).

Option = POST

The command CNCHECK,POST solves the initial contact configuration in one substep. After issuing this command, you can postprocess the contact result items as you would for any other converged load step; however, only the contact status, contact penetration or gap, and contact pressure will have meaningful values. Other contact quantities (friction stress, sliding distance, chattering) will be available but are not useful.

Because Option = POST forces a solve operation, the PrepPost (PP) license does not work with CNCHECK,POST.

If CNCHECK,POST is issued within the solution processor, the SOLVE command that solves the first load step of your analysis should appear in a different step, as shown in the following example:

/SOLU
CNCHECK,POST
FINISH
. . .

/SOLU
SOLVE
FINISH
. . .

CNCHECK,POST writes initial contact results to a results file named Jobname.RCN. When postprocessing the initial contact state, you need to explicitly read results from this file using the FILE and SET,FIRST commands in POST1 to properly read the corresponding contact data. Otherwise, the results file may be read improperly. The following example shows a valid command sequence for plotting the initial contact gap:

/SOLU
CNCHECK,POST
FINISH
/POST1
FILE,Jobname,RCN
SET,FIRST
PLNSOL,CONT,GAP,0,1
FINISH
. . .

Option = ADJUST

You can issue CNCHECK,ADJUST to physically move contact nodes to the target surface. See Physically Moving Contact Nodes Towards the Target Surface in the Contact Technology Guide for more information. Similar to the POST option, if CNCHECK,ADJUST is issued within the solution processor, the SOLVE command that solves the first load step of your analysis should appear in a different step:

/SOLU
CNCHECK,ADJUST
FINISH
. . .

/SOLU
SOLVE
FINISH
. . .

Option = RESET

The command CNCHECK,RESET allows you to reset all but a few key options and real constants associated with the specified contact pairs (RID1, RID2, RINC) to their default values.

The following key options and real constants remain unchanged when this command is issued:

Element typeKey options not affected by RESETReal constants not affected by RESET
TARGE169, TARGE170KEYOPT(2), KEYOPT(3)R1, R2
CONTA171, CONTA172KEYOPT(1), KEYOPT(3)R1, R2
CONTA173, CONTA174, CONTA175, CONTA176, CONTA177KEYOPT(1)R1, R2

Option = AUTO

The command CNCHECK,AUTO automatically changes certain default or undefined key options and real constants to optimized settings or values. The changes are based on overall contact pair behaviors. In general, this command improves convergence for nonlinear contact analysis.

The tables below list typical KEYOPT and real constant settings implemented by CNCHECK,AUTO. The actually settings implemented for your specific model may vary from what is described here. You should always verify the modified settings by issuing CNCHECK,DETAIL to list current contact pair properties.

KEYOPTDescriptionDefault (0 or blank)CNCHECK,AUTO
1Selects DOF setStructural DOFsAutomatic selection based on DOFs of underlying elements.
2Contact algorithmAugmented Lagrange1- Penalty for rigid-rigid contact [1].
4Location of contact detection pointGauss point2 - Normal to target surface if KEYOPT(2) > 1.
5CNOF/ICONT adjustmentNo adjustment1 - Auto CNOF if tiny gap exists.
6Contact stiffness variationUse default range
1 - Nominal refinement for opening contact or underlying elements having TB plasticity.
or
2 - Aggressive refinement for opening contact and underlying elements having TB plasticity.
7Element level time increment controlNo control1 - Automatic bisection for self contact.
8Assymetric contact selectionNo action2 - Auto selection if KEYOPT(2) > 1.
9Effect of initial penetration or gapInclude all1 - Exclude if KEYOPT(5) = 1, or if ICONT was previously specified.
10Contact stiffness updateBetween load steps2 - Between iterations except when underlying elements are superelements. [2]
  1. Set to 0 if KEYOPT(2) > 1 for debonding.

  2. Set to 0 if underlying elements are superelements, or if KEYOPT(9) = 2 was previously specified.

Real ConstantsDescriptionDefaultCNCHECK,AUTO
No.Name
3FKNNormal penalty stiffness factor1Set to 5 if KEYOPT(9) = 2 (ramp initial penetration) and KEYOPT(10) > 0.
6PINBPinball regionsee [1]Cut in half if spurious contact is detected or contact searching is slow.
14TCCThermal contact conductance0Calculated as a function of highest conductivity of underlying element and overall model size.
19ECCElectric contact conductance0Calculated as a function of highest permitivity or lowest resistivity of underlying element and overall model size.
26MCCMagnetic contact permeance0Calculated as a function of highest emissivity of underlying element and overall model size.
  1. PINB default depends on contact behavior (rigid vs. flexible target), NLGEOM,ON or OFF, KEYOPT(9) setting, KEYOPT(12) setting, and the value of real constant CNOF (see Using PINB).

CNCHECK,AUTO also sets PRED,OFF for the case of a force-distributed constraint defined via MPC contact.

Removing or Unselecting Contact and Target Elements

For performance reasons, the program uses a subset of nodes and elements based on the specified contact regions (RID1, RID2, RINC) when executing CNCHECK,POST or CNCHECK,ADJUST.

You can issue CNCHECK,TRIM or CNCHECK,UNSEL to remove or unselect contact and target elements which are in far-field (that is, open and not near contact), or even in near field if aggressive trimming logic is used (TRlevel = AGGRE).

Menu Paths

Main Menu> Preprocessor> Modeling> Create> Contact Pair

Release 14.0 - © 2011 SAS IP, Inc. All rights reserved.