CNTSTB

Format

CNTINT and GAPINT continuation lines can coexist in one CNTSTB card. CTID and PID can be identical in one CNTSTB card, as well.

Example

Definitions

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 $K_{\text{CSTB}}^{\text{normal}}$ is calculated as:
   $$K_{\text{CSTB}}^{\text{normal}}=\{\begin{array}{c}\text{SCALE}\cdot f\left(t^{*}\right)\cdot K_{\text{CREF}}\text{ if contact opening < LMTGAP}\\ \text{ 0 if contact opening }\ge \text{LMTGAP}\end{array}$$
   Where,

   $K_{\text{CREF}}$

   Reference stiffness for contact stabilization.

   Calculated as:

   • For a contact interface: 10^-4 times the raw stiffness of the base elements of the contact.
   • For a CGAP/CGAPG element: 10^-5 times the closed axial stiffness KA on PGAP.

   $f\left(t^{*}\right)$

   Time-dependent scale factor.

   For time, $t$ in a subcase, $t^{*}$ is calculated as:

   $$t^{*}=\left(t-t_0\right)/\left(t_1-t_0\right)$$
   Where,

   $t_0$

   Time at the start of the subcase.

   $t_1$

   Time at the end of the subcase.

   $f\left(t^{*}\right)$ is calculated using $\text{S0}$ and $\text{S1}$ as $f\left(t^{*}\right)=\text{S0}\left(1-t^{*}\right)+\text{S1}\left(t^{*}\right)$ .

3. When APSTB is YES, the contact tangent stabilization stiffness $K_{\text{CSTB}}^{\text{tangent}}$ is calculated as:
   $$K_{\text{CSTB}}^{\text{tangent}}=\text{TFRAC}\cdot K_{\text{CSTB}}^{\text{normal}}$$
4. The defaults and priority information in conjunction with PARAM,EXPERTNL,CNTSTB for different contact types are:

   Table 1. Contact Stabilizationstabilization is not applicable to FREEZE or TIE Contact

   	LGDISP or (LGDISP+SMDISP) g		SMDISP
   	N2S b/S2S	CGAP/CGAPG	N2S c (CGAPG-core)	S2S	CGAP/CGAPG
   PARAM,EXPERTNL,CNTSTB	Damping d	Artificial Spring e	Artificial Spring e	Damping d	Artificial Spring e
   CNTSTB (Priority a) (Bulk card referenced by Subcase Entry)	Damping (‘CNTINT’ or the first line of CNTSTB Bulk card)	Damping f (‘GAPINT’)	Damping (‘CNTINT’ or the first line of CNTSTB Bulk card)	Damping (‘CNTINT’ or the first line of CNTSTB Bulk card)	Damping f (‘GAPINT’)

   1. When both CNTSTB Subcase/Bulk Data pair and PARAM,EXPERTNL,CNTSTB are defined in a subcase, the CNTSTB Subcase/Bulk Data pair takes priority. For other subcases, the stabilization with the PARAM is effective.
   2. When there are LGDISP subcases in a deck file, N2S contact will be converted to Internally generated contact (different from CGAPG), and the stabilization on N2S contact will be conducted in this category.
   3. CGAPG-core N2S is generated, when N2S contact is defined and there is no LGDISP subcases defined in a deck file. The stabilization on N2S contact will be conducted in this category.
   4. In this case, the stabilization activated with the PARAM is consistent with the stabilization activated with default settings of the CNTSTB Bulk Data Entry.
   5. The artificial spring stiffness is determined by:
      $$K_{as}=\max \left\{0.01K\left({10}^{-6t}-{10}^{-6}\right),0.0\right\}$$
      Where,

      $K_{as}$

      Artificial spring stiffness used to stabilize the gap elements.

      $K$

      Reference gap stiffness, generally it represents the stiffness of surrounding elements.

      $t$

      Global analysis time.

   6. The data defined in the first line of this card does not apply on CGAP/CGAPG elements. In order to apply damping stabilization on these elements, continuation lines with ‘GAPINT’ flag must be defined and referenced.
   7. SMDISP+LGDISP indicates models which contain both SMDISP subcases and LGDISP subcases in the same model.
5. Contact stabilization introduces artificial energy that can delay the open-to-close and close-to-open transitions, and it should be used with caution.
6. This card is represented as a load collector in HyperMesh.