CNTSTB

Bulk Data Entry

CNTSTB – Parameters for Stabilization Control of Surface-to-Surface (S2S) Contact and Large Displacement Node-to-Surface (N2S) Contact

Description

Defines parameters for stabilization control of surface-to-surface contact and large displacement node-to-surface contact. A CNTSTB Bulk Data entry should be referenced by a CNTSTB Subcase Information entry to be applied in a particular subcase.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
CNTSTB	ID		APSTB	LMTGAP		S0	S1
	SCALE	TFRAC

The following continuation line (beginning with the CNTINT flag) is used to define another set of stabilization parameters, which overrides the set of parameters above, for a specific contact interface (CTID). It can be repeated as required.

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
	CNTINT	CTID	APSTB	LMTGAP		SO	S1
	SCALE	TFRAC

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
CNTSTB	99		NO
	CNTINT	51	YES
		0.01
	CNTINT	52	YES
	10.0	0.01

Field	Contents
ID	Each CNTSTB bulk data entry should have a unique identification number. No default (Integer > 0)
APSTB	Head flag indicating if contact stabilization is activated. No default YES – contact stabilization effect is activated. NO – contact stabilization effect is deactivated. Note: All the fields following APSTB should be blank, if APSTB is set to NO.
LMTGAP	Contact opening threshold for stabilization. Stabilization becomes zero when contact opening is greater than or equal to this value. Default = blank Blank – the threshold is calculated automatically based on characteristic edge lengths at the contact surfaces. Real > 0.0 – specified threshold value.
S0	Scale factor for stabilization coefficient at the start of a subcase. Default = 1.0 (Real > 0.0)
S1	Scale factor for stabilization coefficient at the end of a subcase. See Comment 5. Default = 0.0 (Real > 0.0)
SCALE	Stabilization coefficient scale factor. Default = 1.0 (Real > 0.0)
TFRAC	Factor for scaling tangential stabilization with respect to normal stabilization. Default = 0.1 (Real > 0.0)
CNTINT	Defines the start of a continuation line used to specify another set of stabilization parameters, which overrides the set of parameters defined above, for a specific contact interface (CTID). It can be repeated as required.
CTID	Contact interface identification number. No default (Integer > 0)

Comments

1.	The CNTSTB bulk data entry is selected by the CNTSTB Subcase Information entry.

2.	When APSTB is YES, the contact normal stabilization stiffness is calculated as:

cntstb_eq

Where, KCREF is automatically calculated reference stiffness (10-5 times the contact penalty stiffness) for contact stabilization, and f (t*) is the time-dependent scale factor.

For time, t in a subcase, t* is calculated as .

Where, t0 is the time at the start of the subcase and t1 is the time at the end of the subcase.

f (t*) is calculated using S0 and S1 as f (t*) = S0 * (1 - t*) + S1 * t*.

3.	When APSTB is YES, the contact tangent stabilization stiffness is calculated as:

4.	The defaults and priority information in conjunction with PARAM,EXPERTNL,CNTSTB for different contact types are as follows:

Contact Stabilization

Stabilization is not applicable to FREEZE or TIE Contact.

	Model without LGDISP analysis		Model with LGDISP analysis
	N2S (CGAPG core)	S2S (GAPSS core)	N2S (GAPSS core)	S2S (GAPSS core)
PARAM,EXPERTNL,CNTSTB	Effective**	Effective*	Effective*	Effective*
CNTSTB (Bulk card referenced by Subcase entry)	Ineffective	Effective	Effective	Effective
PARAM,EXPERTNL,CNTSTB + CNTSTB (Bulk card referenced by Subcase entry)	Stabilization with the PARAM is effective**	For the subcase that references CNTSTB (Bulk Data), stabilization with the BULK card is effective; For other subcases, stabilization with the PARAM is effective.*	For the subcase that references CNTSTB (Bulk Data), stabilization with the BULK card is effective; For other subcases, stabilization with the PARAM is effective.*	For the subcase that references CNTSTB (Bulk Data), stabilization with the BULK card is effective; For other subcases, stabilization with the PARAM is effective.*

* For contacts with "GAPSS core", the stabilization activated with the PARAM is consistent with the stabilization activated with default settings of the CNTSTB Bulk Data Entry.

** For contacts with "CGAPG core", the stabilization can only be activated with the PARAM, and both normal and tangential stabilizations are non-zero, if the PARAM is specified in the model.

5.	Contact stabilization in the last step (S1) may help if there is no tangential resistance at the contact interface and if parts are only held together by contact.

6.	This card is represented as a loadcollector in HyperMesh.