The CNCHECK command provides initial contact status information for both pair-based contact and general contact. The format of the command is:

CNCHECK,Option,RID1,RID2,RINC,InterType,TRlevel,CGAP,CPEN,IOFF

For general contact (InterType = GCN), RID1 and RID2 are section IDs associated with general contact surfaces instead of real constant IDs (as for pair-based contact). If RINC = 0, the Option is performed between the two sections, RID1 and RID2. If RINC > 0, the Option is performed among all specified sections (RID1 to RID2 with increment of RINC).

Following is a list of Option labels that are valid for general contact.

When InterType, RID1, RID2, and RINC are not specified, the CNCHECK command provides and/or adjusts the initial contact status for both pair-based and general contact definitions.

The NLHIST command enables you to monitor general contact information during the solution. Before starting the solution, issue the appropriate NLHIST,GCN commands to specify the contact result items (such as contact penetration or gap, contact normal stiffness, and so on) that you want to track. The resulting data are written to a file named Jobname.nlh.

The user-specified name (Name argument) that you input on the NLHIST command is used to create a parameter for the result item. This enables you to monitor and reuse the contact tracking parameter during solution.

As an example, the following command monitors the maximum contact pressure on a general contact surface with section ID = 101:

NLHIST,GCN,PRESSURE,CONT,PRES,101   ! PRESSURE is a user-specified name

For more information, refer to the NLHIST command description in the Command Reference.

Use the command NLDIAG,CONT to monitor contact diagnostic information during the solution. This feature tracks the same contact information available through NLHIST for all defined contact pairs according to a specified frequency (each iteration, substep, or load step). The resulting output is stored in a text file named Jobname.cnd.

Contact pair ID is one of the items listed In the Jobname.cnd file. A positive contact pair ID refers to a real constant ID for a pair-based contact definition. A negative contact pair ID refers to a section ID of a surface in a general contact definition.

For more information, refer to the NLDIAG command description in the Command Reference.

The GCGEN command offers the easiest method for defining general contact. However, any general contact element type can be created manually instead of through GCGEN.

To create general contact elements manually, create the contact elements as you would for pair-based contact (see Generating Contact Elements), but assign a zero real constant ID (REAL,0) and a zero material ID (MAT,0). You must also assign a unique section ID (SECNUM) and a unique element type ID (TYPE) to identify the elements in each general contact surface. This is similar to the procedure described for creating rigid target surfaces.

Pair-based contact and general contact can coexist in the same model. However, you can easily convert the contact pairs to the general contact definition if desired. To achieve this, use EMODIF commands to assign a zero real constant ID and a zero material ID to the selected contact or target elements:

EMOD,ALL,REAL,GCN
EMOD,ALL,MAT,GCN

This functionality can be useful in the Ansys Workbench application. As an example, consider an asymmetric contact pair defined by Ansys Workbench with REALID = CID, MATID = CID, contact element type = CID, and target element type = TID. The following command sequence converts the pair-based contact to general contact:

ESEL,S,REAL,,CID            ! Select contact pair
EMOD,ALL,REAL,GCN           ! Assign 0 real constant ID to elements
EMOD,ALL,MAT,GCN            ! Assign 0 material ID to elements
ESEL,S,TYPE,,CID            ! Select contact elements
EMOD,ALL,SECN,CID           ! Assign section ID = CID to elements
ET,TID,174                  ! Switch target element type to contact element type 
                            ! for deformable contact
ESEL,S,TYPE,,TID            ! Select contact elements
EMOD,ALL,SECN,TID           ! Assign section ID = TID to elements
EMOD,ALL,REAL,GCN           ! Assign real constant ID = 0 (for general contact)
GCDEF,EXCL,CID,ALL          ! Exclude interaction associated with CID
GCDEF,EXCL,TID,ALL          ! Exclude interaction associated with TID
GCDEF,ASYM,CID,TID,CID,CID  ! Define interaction associated with CID/TID
TB,INTER,CID,,,TBOPT        ! Define interface behavior

The following example demonstrates conversion of pair-based contact to general contact for symmetric contact pairs defined by Ansys Workbench with REALID = CID1/CID2, MATID = CID1, contact element type = CID1/CID2, and target element type = TID1/TID2:

ESEL,S,TYPE,,CID1             ! Select contact elements associated with CID1
EMOD,ALL,REAL,GCN             ! Assign 0 real constant ID to elements
EMOD,ALL,MAT,GCN              ! Assign 0 material ID to elements
EMOD,ALL,SECN,CID1            ! Assign section ID = CID1 to elements
ESEL,S,TYPE,,CID2             ! Select contact elements associated with CID2
EMOD,ALL,REAL,GCN             ! Assign 0 real constant ID to elements
EMOD,ALL,MAT,GCN              ! Assign 0 material ID to elements
EMOD,ALL,SECN,CID2            ! Assign section ID = CID2 to elements
ESEL,S,TYPE,,TID1             ! Select target elements associated with TID1
ESEL,A,TYPE,,TID2             ! Select target elements associated with TID2
EDEL,ALL                             ! Delete target elements (no longer needed)
GCDEF,EXCL,CID1,ALL                  ! Exclude interaction associated with CID1
GCDEF,EXCL,CID2,ALL                  ! Exclude interaction associated with CID2
GCDEF,SYMM,CID1,CID2,CID1,CID1       ! Define symmetric interaction associated with CID1/CID2
TB,INTER,CID1,,,TBOPT                ! Define interface behavior