TIE

Bulk Data Entry Defines a tied contact.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
TIE	`TID`	`PID`	`SSID`	`MSID`	`DOF`	`SRCHDIS`	`ADJUST`
	`DISCRET`			`GSETID`	`ROT`

Example

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
TIE	5		7	8		0.01
	N25			2

Definitions

Field	Contents	SI Unit Example
`TID`	Tied interface identification number. 1 (Integer > 0)
`PID`	Identification number of a Property entry defined in Geometric Nonlinear Analysis ( Radioss Integration). This field is only valid for Geometric Nonlinear Analysis (ANALYSIS=`EXPDYN`). (Integer > 0)
`SSID`	Secondary entity identification. 2 3 Integer Specifies an identification number for this entity. <String> Specifies a user-defined string label for this entity. 12 (Integer > 0 or <String>)
`MSID`	Main entity identification. 2 3 Integer Specifies an identification number for this entity. <String> Specifies a user-defined string label for this entity. 12 (Integer > 0 or <String>)
`DOF`	Defines the degrees-of-freedom (component numbers) that are tied together in MPC-based TIE contact. Default = 123 (Integer, up to six unique digits (0 < digit ≤ 6) may be placed in the field with no embedded blanks for grid points. The components are in the output coordinate system referenced by the secondary grid points).
`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. Default = Half of the main element size (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. 5 NO (Default) No adjustment. 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.
`DISCRET`	Discretization approach type for the construction of contact elements. 2 3 N2S Node-to-surface discretization. S2S Surface-to-surface discretization. N2N Node-to-node discretization. 3 11 blank (Default) Surface-to-surface discretization if the secondary is not a set of grids and there is no heat transfer analysis; node-to-surface discretization, otherwise.
`GSETID`	Identifies a SET entry that references grid points of the secondary entity that are to be included in the TIE contact regardless of the search distance. Therefore, for any grid points identified via `GSETID`, if a corresponding main surface is available, then a corresponding TIE contact is generated regardless of the `SRCHDIS` field value. This grid set should always be a subset of the grids in the secondary entity (identified by the `SSID` field). The `GSETID` field is not supported for N2N discretization. Integer Specifies an identification number for this entity. <String> Specifies a user-defined string label for this entity. 12 blank (Default) (Integer > 0 or <String> or blank)
`ROT`	Constraining rotational degrees of freedom for TIE contact. 13 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 a shell. For Explicit Analysis only.

Comments - Small Displacement Nonlinear Analysis

A TIE Bulk Data Entry should have a unique ID when compared to all CONTACT Bulk Data Entries. The TIE Bulk Data Entry is internally converted to CONTACT Bulk Data with FREEZE option.
The secondary entity (SSID) always consists of grid nodes. It may be specified as:
- a set of grid nodes defined using SET card
- a surface defined using SURF card (the secondary nodes are picked from the respective nodes of the SURF faces)
- a set of elements (shells or solids) defined using SET card. 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.
- OptiStruct will error out, if the structural side is set as Secondary in MPC-based TIE contact for Fluid-Structure model.
- DISCRET=N2S is recommended if the secondary entity is a set of grids (nodes) or a set of solid elements. For more information, refer to Contact Discretization in the User Guide.
The main entity (MSID) may be defined as:
- a surface defined using SURF card
- a set of elements (shells or solids) defined using SET card. For sets of 3D solids, element faces on the surface are automatically found and selected as main surface.
- For N2N discretization, MSID should refer to a GRID set defined by the SET entry.
TIE element is created with the same structure as a CONTACT element of TYPE=FREEZE. TIE element enforces zero relative motion on the contact surface - the contact gap opening remains fixed at the original value and the sliding distance is forced to be zero. Also, rotations at the secondary node are matched to the rotations of the main patch. For more information, refer to Contact Discretization in the User Guide.
For more information regarding SRCHDIS and ADJUST, refer to Contact Interface Parameters (Contact Control) in the User Guide.
Contact stabilization for surface-to-surface contact and node-to-surface contact can be activated using the CNTSTB Subcase Information Entry and the CNTSTB Bulk Data Entry. Additionally, the PARAM, EXPERTNL Bulk Data Entry can be used to activate contact stabilization. The CNTSTB Bulk Data Entry parameters override the parameter values for a particular subcase.
Two types of TIE contacts are available, PENALTY-based and MPC-based. The two types can be switched using CONTPRM,TIE,PENALTY/MPC. The MPC-based TIE uses multi-point constraints to define a tied contact between the main and secondary surfaces. Additionally, the MPC's can be output to <filename>_contmpc.fem using CONTPRM, CONTMPC, YES. If CONTPRM,TIE,MPC is specified, all the TIE contacts in the model are defined using the MPC-based method. For more information regarding SRCHDIS and ADJUST, refer to Lagrange Multipliers (MPC-based) in the User Guide.
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.

The following table illustrates support information for TIE contacts:

TIE Contact	Linear Static	Linear Transient	Nonlinear Static		Nonlinear Transient
TIE Contact	Linear Static	Linear Transient	SMDISP	LGDISP	Implicit (SMDISP)	Implicit (LGDISP)	Explicit
Penalty-based TIE	Yes (Default)	Yes (Default)	Yes (Default)	Yes (Default)	Yes (Default)	Yes (Default)	Yes (Auto)
MPC-based TIE	Yes (Optional)	Yes (Optional)	Yes (Optional)	Yes (Optional)	Yes (Optional)	Yes (Optional)	Yes (Default)

MODCHG is currently not supported for MPC-based TIE for both Small and Large Displacement Nonlinear Analysis.

For Implicit Analysis, PENALTY-based TIE is the default. Whereas, for Explicit Analysis, MPC-based TIE is the default. For Explicit Analysis, if OptiStruct detects the model contains over-constraint conditions, then the related TIE is switched to PENALTY-based TIE automatically.
N2N discretization is currently only supported for Small Displacement Nonlinear Analysis.
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.

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
TIE Contact	Linear Static	Linear 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)

This card is represented as a group in HyperMesh.