CONTACT

Bulk Data Entry

CONTACT – Contact Interface Definition

Description

Defines a contact interface for Small Displacement Nonlinear Analysis (NLSTAT), Nonlinear Transient Dynamics (NLGEOM), and Contact-based Thermal Analysis (HEAT).

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
CONTACT	CTID	PID/ TYPE/ MU1	SSID	MSID	MORIENT	SRCHDIS	ADJUST	CLEARANCE
	DISCRET	TRACK

The following continuation line is used to define surface smoothing for S2S contact interface. It can be repeated as required.

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	SMOOTH	SMSIDE	SMREG

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

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

Field	Contents
CTID	Contact interface identification number. (Integer > 0)
PID	Property identification number of a PCONT or PCONTX entry. (Integer > 0)
TYPE	Choose type of contact without pointing to contact property – respective default property settings will be used. Default settings can be changed using CONTPRM. See Comment 4. SLIDE – 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). Default = SLIDE (SLIDE, STICK, or FREEZE)
MU1	Coefficient of static friction (µs). See Comment 5. (0.0 < Real < 1.0)
SSID	Slave entity identification number. See Comments 1, 2 and 10. (Integer > 0)
MSID	Master entity identification number. See Comments 1, 2 and 10. (Integer > 0)
MORIENT	Orientation of contact “pushout” force from master surface. Applies only to masters that consist of shell elements or patches of grids. Masters defined on solid elements always push outwards irrespective of this flag. See Comment 6. OPENGAP – The contact interface is assumed open. OVERLAP – Slave and master bodies overlap. NORM – Contact force is oriented along the vector normal to the master surface. REVNORM – Contact force is oriented opposite to the default vector normal to the master surface. Default = OPENGAP (OPENGAP, OVERLAP, NORM or REVNORM).
SRCHDIS	Search distance criterion for creating contact condition. When specified, only slave nodes that are within SRCHDIS distance from master surface will have contact condition checked. See Comment 6. Default = twice the average edge length on the master surface. For FREEZE contact, half the average edge length. (Real > 0 or blank)
ADJUST	Adjustment of slave nodes onto the master surface at the start of a simulation. See Comment 6. <NO, AUTO, Real > 0.0, or Integer > 0> Default = NO. NO – no adjustment. AUTO – A real value equal to 5% of the average edge length on the master 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 slave nodes (for which contact elements have been created). These slave nodes (with created contact elements) are then adjusted onto the master 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 slave entity which also belong to this SET will be selected for adjustment.
CLEARANCE	Initial gap opening between master and slave, irrespective of the actual distance between the nodes. See Comment 6. Default = blank (Real or blank)
DISCRET	Discretization approach type for the construction of contact elements. See Comment 1. <N2S, S2S, blank> Default = blank. N2S – node-to-surface discretization. S2S – surface-to-surface discretization. blank – surface-to-surface discretization if it is a FREEZE contact, the slave is not a set of grids and there is no heat transfer analysis; node-to-surface discretization, otherwise.
TRACK	Activates Finite-Sliding contact. See Comment 14. <SMALL, FINITE, CONSLI> Default = SMALL SMALL – Small-Sliding contact is activated. This contact option applicable to contacts with small relative sliding between the master and slave. FINITE – Finite-Sliding contact is activated. This contact option allows for the incorporation of finite (large) relative sliding between the master and slave. CONSLI – Continuous-sliding contact is activated. This contact option allows for the incorporation of continuous (large) relative sliding between the master and slave. See Comment 15.
SMOOTH	Continuation lines for surface smoothing definition flag. See Comment 6.
SMSIDE	Master and/or Slave side(s) of the contact interface to be smoothed. See Comment 10. <MASTER, SLAVE, or BOTH> No default. MASTER – the Master side of the contact interface. SLAVE – the Slave side of the contact interface. BOTH – both Master and Slave sides of the contact interface.
SMREG	Specifies the region of the Master/Slave side to be smoothed. See Comment 10. <ALL or Integer > 0> Default = ALL. ALL – the whole Master/Slave surface. Integer > 0 – identification number of a region (SURF bulk data entry) at the Master/Slave surface.

Comments for Small Displacement Nonlinear Analysis

1.	A general set of guidelines for slave/master selection are as follows:

•	Select the surface with finer mesh as the slave and the other as the master

•	Select the smaller surface as the slave and the other as the master

•	Select the softer surface as the slave and the other as the master

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

2.	The slave 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 slave nodes are picked from the respective nodes of the SURF faces)

•	a set of elements (shells or solids) defined using SET(ELEM, ..) command. Slave 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 slave entity is a set of grids (nodes) or a set of solid elements.

3.	The master 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 master surface.

4.	For information on the different contact interfaces (TYPE field options), refer to Contact Interface Types in the User's Guide.

MU1 directly on the CONTACT card allows for simplified specification of frictional contacts. Note that this implies MU2=MU1, unless MU2 is specified explicitly on the CONTPRM card. Also note that 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 Geometric Nonlinear 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's Guide.

6.	For information regarding the different contact parameters (ADJUST, CLEARANCE, MORIENT, TRACK, SMOOTH, SRCHDIS, GPAD), refer to Contact Interface Parameters in the User's Guide.

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.

Comments for geometric nonlinear analysis (ANALYSIS = NLGEOM) subcases

CONTACT models an interface between a master surface and a set of slave grid points. A grid point can be at the same time as a slave and a master node. Each slave grid point can impact each master segment; except if it is connected to the impacted master segment. A grid point can impact on more than one segment. A grid point can impact on the two sides, on the edges, and on the corners of each segment. The contact uses a fast search algorithm without limitations.

The main limitations of this interface follow: a) the time step in an explicit analysis is reduced in case of high impact speed or contacts with small gap; b) the contact may not work properly, if used with a rigid body at high impact speed or rigid body with small gap; and c) the contact does not solve edge to edge contact.

9.	Additional control can be applied to the CONTACT definition in geometric nonlinear subcases through CONTPRM and PCONTX. These definitions are ignored in all other subcases. A geometric nonlinear subcase is one that has an ANALYSIS = NLGEOM entry in the subcase definition.

10.	For basic Master and Slave information, see Comment 1. TYPE=FREEZE is implemented as a TIE kinematic condition for large deformation subcases.

11.	For implicit analysis, modified settings that improve the contact convergence are recommended. See CONTPRM and PCONTX.

Comment for Contact-based Thermal Analysis

12.	Thermal-structural analysis problems involving contact are fully coupled since contact status changes thermal conductivity. Refer to Contact-based Thermal Analysis in the User’s Guide for more information.

General Comments

13.	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.

14.	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 in the User's Guide.

15.

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.

16.	This card is represented as a group in HyperMesh.