# CONTACT

Bulk Data Entry Defines a contact interface.

Attention: Valid for Implicit and Explicit Analysis

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CONTACT CTID PID/

TYPE

/MU1

SSID MSID MORIENT SRCHDIS ADJUST CLEARANCE
DISCRET TRACK CORNER   ROT SORIENT
The following continuation line is used to define surface smoothing for the contact interface. It can be repeated as required.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
+ SMOOTH SMSIDE SMREG SMTYPE
±   SMTPAR1 SMTPAR2 SMTPAR3 SMTPAR4 SMTPAR5 SMTPAR6
The following continuation line is used to define surface properties which can be used to trigger edge to edge contact.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
+ PSURF PSID1 PSID2
The following continuation line is used to define cohesive material property for cohesive zone contact.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
+ COHE MCOHEDID COHEGSET
The following continuation line is used to define the reference point for contact moment calculation.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
+ MNTREF REFPOINT/X Y Z
The following continuation lines are used to define auto-contact settings for Explicit Dynamic Analysis (ANALYSIS=NLEXPL).
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
+ ACTIVA IDS1 IDM1
IDS2 IDM2
+ DEACTIVA IDS5 IDM6
IDS7 IDM7
+ PCONT MSID1 SSID1 PID1
MSID2 SSID2 PID2
etc. etc. etc.
+ PSURF SID1 PSID1
SID2 PSID2

## Example 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CONTACT 5 SLIDE 7 8
N2S

## Example 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CONTACT 5 SLIDE 7 8
S2S
SMOOTH SECOND 71
SMOOTH SECOND 72
SMOOTH MAIN ALL

## Example 3 (Auto-Contact)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CONTACT 23 AUTO
ACTIVA ALL
PSURF ALL 11

## Definitions

Field Contents SI Unit Example
CTID Contact interface identification number.

(Integer > 0)

PID Property identification of a PCONT Bulk Data Entry.
Integer
Specifies an identification number for this entity.
This is supported for PCONT and PCONTX entries.
<String>
Specifies a user-defined string label for this entity.
This is supported only for the PCONT entry.

(Integer > 0 or <String> (only for PCONT))

TYPE Choose type of contact without pointing to contact property - respective default property settings will be used. Default settings can be changed using CONTPRM. 4
SLIDE (Default)
Sliding contact (applied to both open and closed contacts).
STICK
Contact with stick condition (applies to closed contacts only).
FREEZE
Enforced zero relative displacements on the contact interface (applies to both closed and open contacts).
AUTO
Auto Contact (only applicable to Explicit Dynamic Analysis – ANALYSIS=NLEXPL). 20

MU1 Coefficient of static friction ( $\mu$ ). 5

(0.0 ≤ Real < 1.0)

SSID Secondary entity identification. 1 2 10
Integer
Specifies an identification number for this entity.
<String>
Specifies a user-defined string label for this entity. 23
(Integer > 0 or <String>)

MSID Main entity identification. 1 2 10
Integer
Specifies an identification number for this entity.
<String>
Specifies a user-defined string label for this entity. 23
(Integer > 0 or <String>)

MORIENT Orientation of contact "pushout" force from main surface. Applies only to mains that consist of shell elements or patches of grids. Mains defined on solid elements always push outwards irrespective of this flag. 6 19
OPENGAP
The contact interface is assumed open.
Not supported for TRACK=FINITE/CONSLI.
OVERLAP
Secondary and main bodies overlap.
Not supported for TRACK=FINITE/CONSLI.
NORM
Contact force is oriented along the vector normal to the main surface.
REVNORM
Contact force is oriented opposite to the default vector normal to the main surface.

Default = OPENGAP (if TRACK is not set to FINITE/CONSLI) or NORMAL (if TRACK=FINITE/CONSLI)

SRCHDIS Search distance criterion for creating contact condition. When specified, only secondary nodes that are within SRCHDIS distance from main surface will have contact condition checked. 6

Default = Twice the average edge length on the main surface. For FREEZE contact, half the average edge length. (Real > 0 or blank)

For Node-to-Node (N2N) discretization, the default is 0.0

ADJUST Adjustment of secondary nodes onto the main surface at the start of a simulation. 6
NO (Default)
AUTO
A real value equal to 5% of the average edge length on the main surface is internally assigned as the depth criterion.
Real ≥ 0.0
Value of the depth criterion which defines the zone in which a search is conducted for secondary nodes (for which contact elements have been created). These secondary nodes (with created contact elements) are then adjusted onto the main surface. The assigned depth criterion is used to define the searching zone in the pushout direction.
Integer > 0
Identification number of a SET entry with TYPE = GRID. Only the nodes on the secondary entity which also belong to this SET will be selected for adjustment.

For Node-to-Node (N2N) discretization, the default is NO and Real value can be specified for the depth criterion, similar to other discretization types. AUTO and Integer do not apply for N2N discretization.

CLEARANCE
Real
Initial gap opening between main and secondary, irrespective of the actual distance between the nodes. 6
Integer
References the identification number of a CLRNC Bulk Data Entry. This is used to define threaded bolt geometry and specify the part of the contact interface to be identified as a threaded bolt. 25
blank (Default)
Clearance is not defined.

DISCRET Discretization approach type for the construction of contact elements. 1
N2S
Node-to-surface discretization.
S2S
Surface-to-surface discretization.
N2N
Node-to-node discretization. 3 15
blank (Default)
S2S: Used if FREEZE contacts with secondary are not defined as a set of grids and if there is no heat transfer analysis involved.
N2S: In all other cases.

TRACK Activates Finite-Sliding contact. 10
SMALL (Default)
Small-Sliding contact is activated. This contact option applicable to contacts with small relative sliding between the main and secondary.
FINITE
Finite-Sliding contact is activated. This contact option allows for the incorporation of finite (large) relative sliding between the main and secondary.
CONSLI
Continuous-sliding contact is activated. This contact option allows for the incorporation of continuous (large) relative sliding between the main and secondary. 11

ROT Constraining rotational degrees of freedom for N2S and S2S FREEZE contact. 24
YES (Default)
Rotational degrees of freedom are constrained.
NO
Rotational degrees of freedom are not constrained.
DRILL
Rotational DOFs are constrained and moments on secondary nodes are transferred to the main side as force if the main side is shell (for explicit analysis only).

SORIENT Orientation of contact force applied on the secondary surface (which should be in the same direction as the pushout force from the main surface). This field is only relevant when the secondary surface consists of shell elements with S2S (CONSLI) contact. 19
REVNORM
Contact force is oriented along the vector normal to the secondary surface.
NORM (Default)
Contact force is oriented opposite to the default vector normal to the secondary surface.

CORNER Corner treatment for the secondary surface of N2S and S2S contacts. 12
Blank (Default)
AUTO for S2S and NO for N2S contact.
NO
No corner treatment.
AUTO
Corner treatment is turned on. 30 degree will be used as default break angle.
0.0 ≤ Real < 180.0
Degree value of break angle criterion which defines the break angle between the two surface elements that share an edge. The surface area around a secondary node will be broken into surface patches at the edges that satisfy the break angle criterion.

SMOOTH Continuation lines for surface smoothing definition flag. 6
SMSIDE Main and/or secondary side(s) of the contact interface to be smoothed. 6
MAIN
Main side of the contact interface.
SECOND
Secondary side of the contact interface.
BOTH
Both the main and secondary sides of the contact interface.

No default

SMREG Specifies the region at the main/secondary surface to be smoothed. 6
ALL (Default)
The entire main/secondary surface.
Integer > 0
Identification number of a SURF Bulk Data Entry, which can be the same as or a portion of the main/secondary surface. The error will happen if the SURF ID specified here is outside of the main or secondary surface.

SMTYPE Specifies the smoothing method. 6
CIRCUM
The region is smoothed with a condition that the grids on this region are located on a circumferential surface.
SPHERIC
The region is smoothed with a condition that the grids on this region are located on a spherical surface.
Blank (Default)
The region is smoothed by using a Bezier surface.

SMPARi Specifies the smoothing parameters if SMTYPE = CIRCUM/SPHERIC. 6

If SMTYPE = CIRCUM: SMTPAR1 through SMTPAR6 are specified to define the axis of symmetry passing through two points (SMTPAR1, SMTPAR2, SMTPAR3) and (SMTPAR4, SMTPAR5, SMTPAR6).

If SMTYPE = SPHERIC: SMTPAR1 through SMTPAR3 are specified to define the center point (SMTPAR1, SMTPAR2, SMTPAR3) of the spherical surface. SMTPAR4 through SMTPAR6 should not be specified.

No default (Real)

Note: This continuation line should not be present if SMTYPE = Blank.

PSURF Continuation line for surface property assignment. Only supported for explicit analysis.
PSID1 The PSURF entry ID which is used to define the secondary surface property.

No default (Integer > 0)

PSID2 The PSURF entry ID which is used to define the main surface property.

No default (Integer > 0)

COHE Continuation line for cohesive material. 18
MCOHEDID Identification number of MCOHED card that is referenced by the current contact.

No default (Integer > 0)

COHEGSET Cohered grid set. 14
CURRENT
Closed contact nodes are cohered, open contact nodes will be cohered after they closed during analysis.
ORIGIN
Only the initially closed contact nodes are cohered. Initially open contact nodes will not be cohered even if they become closed during the analysis.
ALL (Default)
All secondary nodes in the contact are cohered, (regardless of open/close status).
Integer > 0
Refers to a grid SET ID containing nodes belonging to the secondary surface to be cohered. Only the nodes included in the grid set are cohered.

MNTREF Flag indicating that the reference point definition for the contact moment calculation is next.
REFPOINT Reference point definition. 26
GID
ID of the reference grid.
CENTER
Flag indicating that the reference point is the geometric center of the secondary side area in a closed status.
ORIGIN
Flag indicating that the reference point is the origin of the basic coordinate system.
X, Y, Z
X, Y and Z coordinates of a user-defined reference point.
No default (Real, CENTER, or ORIGIN)

ACTIVA Flag indicating that the following fields indicate the surfaces for which the auto-contact is activated. 20 21
IDSi
Integer > 0
References the identification number of Secondary Surface ID for which the contact is to be activated.
ALL
Indicates that contact surfaces are generated automatically for the entire model. IDMi field should be left blank if IDSi is set to ALL.

No default

IDMi
Integer > 0
References the identification number of Main Surface ID for which the contact is to be activated.

No default

DEACTIVA Flag indicating that the following fields indicate the surfaces for which the auto-contact is to be deactivated. 20 22
IDSi
Integer > 0
References the identification number of Secondary Surface ID for which the contact is to be deactivated.

No default

IDMi
Integer > 0
References the identification number of Main Surface ID for which the contact is to be deactivated.

No default

PCONT Flag indicating that the following fields reference contact interfaces to which the corresponding PCONT PID applies.
MSIDi
Integer > 0
References the identification number of a main surface ID for which the PCONT entry is to be applied. Currently, only SURF entry of type ELFACE are supported.
ALL
Indicates that the referenced PCONT entry is applied automatically to all contact interfaces in the model. In this case, the SSIDi field should be left blank.

No default

SSIDi
Integer > 0
References the identification number of a secondary surface ID for which the PCONT entry is to be applied. Currently, only SURF entry of type ELFACE are supported.

No default

PIDi References the identification number of a PCONT entry.

No default (Integer > 0)

PSURF Flag indicating that the following fields reference contact interfaces to which the corresponding PSURF PIDs apply.
SIDi
Integer > 0
References the identification number of main or secondary surface ID for which the PSURF entry is to be applied.
ALL
Indicates that the referenced PSURF entry is applied automatically to all main and secondary surfaces in the model.

No default

PSIDi References the identification number of PSURF entries.

1. A general set of guidelines for secondary/main selection are:
• Select the surface with finer mesh as the secondary and the other as the main.
• Select the smaller surface as the secondary and the other as the main.
• Select the softer surface as the secondary and the other as the main.

For information regarding choosing between N2S and S2S contact, refer to Contact Discretization in the User Guide.

2. The secondary entity (SSID) always consists of grid nodes. It may be specified as:
• A set of grid nodes defined using SET(GRID, ..) command
• A surface defined using SURF command (the secondary nodes are picked from the respective nodes of the SURF faces)
• A set of elements (shells or solids) defined using SET(ELEM, ..) command. Secondary nodes are picked from the respective nodes of the elements in the set. For 3D solids, only nodes on the surface of the solid body are selected; internal nodes are not considered.

DISCRET=N2S is recommended if the secondary entity is a set of grids (nodes) or a set of solid elements.

3. The main entity (MSID) may be defined as:
• A surface defined using SURF command.
• A set of elements (shells or solids) defined using SET(ELEM, ..) command. For sets of 3D solids, element faces on the surface are automatically found and selected as main surface.
• The MSID can be left blank or set the same as SSID to activate Self Contact condition. This is currently supported only for Node-to-Surface (N2S) and Surface-to-Surface (S2S) contact with Continuous Sliding (CONSLI). For further information, refer to Self-Contact in the User Guide.
• For N2N discretization, MSID should refer to a GRID set defined by the SET entry.
4. For information on the different contact interfaces (TYPE field options), refer to Contact Interface Types in the User Guide.
5. MU1 directly on the CONTACT card allows for simplified specification of frictional contacts.
Note: This implies MU2=MU1, unless MU2 is specified explicitly on the CONTPRM card. Also, the value of MU1 assigned on the CONTACT card must be less than 1.0 - to specify higher values of static coefficient of friction, the PCONT card must be used.

If FRIC is not explicitly defined on the PCONTX/PCNTX# entries, the MU1 value on the CONTACT or PCONT entry is used for FRIC in the /INTER entries for Explicit Dynamic Analysis. Otherwise, FRIC on PCONTX/PCNTX# overwrites the MU1 value on CONTACT/PCONT. For further information regarding frictional contact, refer to Friction in the User Guide.

6. For information regarding the different contact parameters (ADJUST, CLEARANCE, MORIENT, TRACK, SMOOTH, SRCHDIS, GPAD), refer to Contact Interface Parameters (Contact Control) in the User Guide.
7. Contact stabilization for Surface-to-Surface Contact and Node-to-Surface contact can be activated using the CNTSTB Subcase Information and CNTSTB Bulk Data Entries. Additionally, PARAM, EXPERTNL,CNTSTB can be used to activate contact stabilization. The CNTSTB Bulk Data parameters override the parameter values for a particular subcase.
8. Thermal-structural analysis problems involving contact are fully coupled since contact status changes thermal conductivity. For further information, refer to Contact-based Thermal Analysis in the User Guide.
9. Applying rotational SPC on nodes which belong to a FREEZE contact should be avoided. Fixing the rotational degrees of freedom will prevent the rotation of these contact nodes even in the case of solid elements.
10. Finite Sliding (TRACK=FINITE) option is currently supported only if TYPE=SLIDE or if friction (via MU1/CONTPRM/PCONT) is defined. For further information, refer to Finite Sliding (TRACK) in the User Guide.
11. In continuous-sliding contact (TRACK=CONSLI), the contact search is conducted for every contact iteration. In the formulation of contact virtual work, every term is updated based on the status in current iteration. The contact tangent stiffness matrix is computed in a consistent way. Continuous-sliding contact is expected to produce more accurate results and in some cases, better convergence robustness, especially when very large sliding and/or distortion are present.
12. Corner treatment is supported for N2S (only for TRACK=CONSLI) and S2S (for all TRACK options) contacts. When corner treatment is turned on (AUTO or Real value), the contact surface around a secondary node may be divided into several continuous surface patches if break angle criteria are satisfied on one or more edges at the node. For each surface patch, a separate contact element will be created for the element stiffness matrix, element force vector and element history variables computation. Corner treatment may improve robustness and accuracy in some cases.
13. The CONTACT entry is supported for:
• Linear and Nonlinear Static Analysis
• Linear and Nonlinear Transient Analysis
• Linear Dynamic Analysis
• Heat Transfer Analysis
• Contact-based Thermal Analysis (HEAT)
14. N2S option should be used to activate large shape change during shape optimization. Currently, large shape change is activated if the model has N2S contact or CGAP/CGAPG/CWELD/CFAST/CSEAM elements.
15. N2N discretization is currently only supported for Small Displacement Nonlinear Analysis.
16. The following comments apply to Edge-to-Edge contact via PSURF field.
• PSURF field is only supported for explicit analysis.
• The secondary side must be surface-based (cannot be grid-based).
• PSURF should be defined for both secondary and main.
• Shell boundary edges are not currently supported.
17. Axisymmetric and plane-strain contacts are supported for axisymmetric elements (CQAXI, CTAXI, and CTRIAX6 elements) and plane-strain solid elements (CQPSTN and CTPSTN elements). The SURF entry can be used to define the Main and Secondary surfaces.
Axisymmetric and plane-strain contacts are currently supported for:
• SMALL (small sliding) for both N2S and S2S discretization
• CONSLI (continuous sliding) for N2S discretization
Axisymmetric and plane-strain contacts are not supported for:
• FINITE (finite sliding)
• CONSLI (continuous sliding) for S2S discretization
• Surface Smoothing
18. Cohesive contact works only for small-sliding (TRACK=SMALL), frictionless (TYPE=SLIDE or MU1=0.0) N2S/S2S contact.
19. In case of implicit analysis, the shell contact surface orientation must be user-defined.

In case of explicit analysis, the shell contact surface orientation is automatically detected. Thus, the user does not need to define consistent orientations on the surface.

20. Auto-Contact is activated by setting the TYPE field to AUTO and is only applicable to Explicit Dynamics (NLEXPL) analysis. ACTIVA continuation line is used to activate auto-contact, and DEACTIVA continuation line is used to deactivate certain contact interfaces from auto-contact. PCONT and PSURF continuation lines can be used to correspondingly activate Contact Properties and Edge Criteria for contact interfaces and surfaces.
21. For ACTIVA, if both IDSi and IDMi are defined, then OptiStruct will internally generate components based on these surfaces and detect all possible contact among them.
For example, if you define:
+, ACTIVA, 1, 2
+, , 3, 4

Then internally separate components are created based on surfaces 1, 2, 3, and 4. Contact is then automatically detected between these components. Self-contact inside each component is also detected.

Each surface can include multiple components (even the entire model can be a single surface). Internally, components are created for any defined surfaces. Component here implies a topologically connected geometry, like a bolt. Therefore, two separate bolts will be treated as two components even if they are defined as a single surface.

22. DEACTIVA is specifically intended to disable unwanted contact inside the model.
For example, if you define:
 +, DEACTIVA, 1, 2
+, , 3, 4

Then contacts between faces in surface 1 and surface 2 are deactivated. Similarly, contact between faces in surface 3 and surface 4 are also deactivated. Self-contact within surface 1 and self contact within surface 2 and so on will not be deactivated. Additionally, contact between surfaces 1 and 3, or contact between surface 1 and 4, etc will not be deactivated.

To explicitly deactivate self-contact for a particular surface, for instance, surface 1, then the following line can be added:
+, DEACTIVA, 1, 2
+, , 3, 4
+, ,1,1
If there are any contact interfaces defined via Standard CONTACT or TIE entries, they will automatically be excluded in Auto-contact. For example,
 +, ACTIVA, ALL
TIE,100,1,2

The contact between surfaces 1 and 2 are excluded. An exception to this is that these exclusions occur only if surfaces 1 and 2 are defined in the ELFACE format. If the surface 1 is a nodal SET, then such surfaces are not excluded.

23. String based labels allow for easier visual identification, including when being referenced by other entries. For more details, refer to String Label Based Input File.
24. For explicit analysis where the main side is shell, if the DRILL option is specified for ROT field of TIE and freeze CONTACT entries, the moment on the secondary side will be transferred to the main nodes as forces (instead of moments) as shown below. For explicit analysis with main side as solids, this is active by default and the ROT field has no effect.
Information for TIE contact.
TIE Contact Linear Static Linear Transient Nonlinear Static Nonlinear Transient
SMDISP LGDISP Implicit (SMDISP) Implicit (LGDISP) Explicit
Rotational DOF (Main side is shell) Yes (Default) Yes (Default) Yes (Default) Yes (Optional via ROT=YES) Yes (Default) Yes (Optional via ROT=YES) Yes (Optional via ROT=YES)
Rotational DOF (Main side is solid) Yes (Optional) Yes (Optional) Yes (Optional) Yes (Optional via ROT=YES) Yes (Optional) Yes (Optional via ROT=YES) Yes (Default)
25. CLRNC ID can be specified on the CLEARANCE field in the CONTACT or PCONT Bulk Data Entry. If there is a conflict, then the CLRNC ID specified on PCONT takes precedence.
26. Contact moment calculation/output can be activated by the MNTREF continuation line. Each contact can have its own reference point for contact moment calculation/output. In a large displacement analysis, the location of a reference point defined by GID or CENTER is updated with deformation.
Supported Analysis Types
Nonlinear Static and Nonlinear Transient, for both small and large displacement analysis types.
Supported Output Types
OPTI (.cntf) only.
27. This card is represented as a group in HyperMesh.