Contact Parameters–Global Pair dialog box

Modeling Object
Name	Sets a unique name for the modeling object.
Label	Sets a unique integer for the modeling object.This label also appears in the Modeling Objects Manager dialog box, and you can filter the objects listed in that dialog box by their label.
Properties
Description	Sets a description for this set of contact parameters.You can optionally click Description to open the Description dialog box. This lets you see more of the text that you type, as well as cut, copy, or paste text.This description appears only on this dialog box.
Card Name	Displays the name of the corresponding solver command or keyword.
Solution Applicability View	Controls the visible options in the dialog box. You can view all options for the BCTPARM bulk data entry or only those applicable to a specified solution.
Properties
To add a parameter to the BCTPARM bulk entry, click Add .To remove a parameter from the BCTPARM bulk entry, click Remove .

General Parameters

Contact Algorithm	METHOD field in the BCTPARM bulk data entry.Specifies the contact algorithm to use.
Interface Behavior	INTRFC field in the BCTPARM bulk data entry.Lets you specify the interface behavior between the source and target region.
Refine Source Mesh Region	REFINE field in the BCTPARM bulk data entry.Controls whether the software refines the mesh on the source region during the contact solution.Select Refine to have the software refine the mesh.Select Do Not Refine to use the original mesh.
Number of Contact Evaluation Points	INTORD field in the BCTPARM bulk data entry.Determines the number of contact evaluation points for a single element face on the source region. The number of contact evaluation points depends on the option you select here as well as on the type of element. Increasing the number of evaluation points can increase the accuracy of your solution. See BCTPARM in the Simcenter Nastran Quick Reference Guide for more information.Select Reduced Number to use a reduced number of evaluation points.Select Increased Number to use a higher number of evaluation points.Select High Number to use a high number of evaluation points.
Export a Preview Bulk Data File	PREVIEW field in the BCTPARM bulk data entriesWrites out a bulk data file that contains dummy:Shell element entries for face locations.PLOTEL entries for edge locations.GRID, property, and material bulk data entries.When you import the preview file, the software uses these dummy entities to display the source and target locations for contact and glue conditions.For more information, see Previewing contact and glue element locations (Simcenter Nastran).
Contact Status	RESET field in the BCTPARM bulk data entry.Controls whether the contact status for a specific subcase starts from the final status of the previous subcase.Select Start from Previous to start the status from the final status of the previous subcase.Select Start from Initial to start the status from an initial state.

Initial Penetration

Initial Penetration / Gap	INIPENE field in the BCTPARM bulk data entry.Controls the definition of the initial gap or penetration of the generated contact elements. Initial penetrations can exist due to geometry or mesh irregularities between source and target faces or edges.Calculate from GeometryEvaluates contact exactly as the geometry is modeled, though corrections may be necessary for gaps or penetrations.Set Penetrations to ZeroResets penetrations to a new initial condition in which there is no interference.Set to Gaps and Penetrations to ZeroResets both gaps and penetrations to a new initial condition in which there is no interference.
Ramp Option for Initial Penetration	IPENRAMP field in the BCTPARM bulk data entry.Controls whether the software ramps the removal of initial penetrations when Initial Penetration / Gap is set to Calculate from Geometry or Set Penetrations to Zero.
Contact Gap Distance	GAPVAL field in the BCTPARM bulk data entry.Defines a constant gap distance between the source region and the target region when Initial Penetration / Gap is set to Set to Gaps and Penetrations to Zero. A negative value indicates that an initial penetration exists that the software will eliminate.
Offset Distance after initial Penetration Action	OFFSET field in the BCTPARM bulk data entry.Specifies a constant offset distance for a contact pair.
Shell Thickness Offset	SHLTHK field in the BCTPARM bulk data entry.Controls how the software handles shell thickness.If you select Include, the software assumes that the contact surface is offset /2 from the nodes defining a shell element.If you select Do not Include, the software does not include the thickness offset in the calculation. This is appropriate if the FE mesh represents the outer surface.
Include Shell Element Z-Offset	ZOFFSET field in the BCTPARM bulk data entry.Controls whether the software includes any shell element z-offset when it determines the contact stiffness.
Initial Node Adjustment Tolerance	ADJUST field in the BCTPARM bulk data entry.Controls whether the software removes an initial separation by moving nodes.The software uses this tolerance to move the source nodes onto the target faces when the absolute value of the initial separation distance is below this value. The adjustment tolerance is computed as Initial Node Adjustment Tolerance * characteristic length.
Time to Resolve Initial Penetrations	TZPENE field in the BCTPARM bulk data entry.Specifies an end time when the software eliminates initial penetrations. Ramping the removal of initial penetrations can help convergence. Note: If you do not specify a time of 0.0, the software eliminates the initial penetrations in the first subcase.

Stiffness

Scale Automatically Calculated Penalty Factors	AUTOSCAL field in the BCTPARM bulk data entry.Lets you specify a scale factor to apply to the stiffness of specific contact pairs if convergence issues occur.
Tangential Penalty Scale Factor	TANSCL field in the BCTPARM bulk data entry.If you do not specify a value for the Penalty Tangential Direction option, you can use this option to scale up or down the tangential penalty factor that the software calculates automatically. You can use this option to scale the stiffness of specific contact pairs if convergence issues occur.
Penalty Normal Direction	PENN field in the BCTPARM bulk data entry.Lets you specify the penalty factor for the normal direction.
Penalty Tangential Direction	PENT field in the BCTPARM bulk data entry.Lets you specify the penalty factor for the tangential direction.
Penalty Factor Units	PENTYP field in the BCTPARM bulk data entry.Lets you control the units in which you define the Penalty Normal Direction and Penalty Tangential Direction values. This affects how the software calculates the contact element stiffness.
Open Contact Stiffness Scale Factor	OPNSTF field in the BCTPARM bulk data entry.Lets you specify the open contact stiffness scale factor.
Adaptive Contact Stiffness	PENADAPT field in the BCTPARM bulk data entry.Controls whether the software adaptively varies the penalty factor between iterations.

Friction

Tangential Stiffness Selection	FRICMOD in the BCTPARM bulk data entry.Specifies the friction behavior to use.
Friction Coefficient 1	FPARA1 parameter of the BCTPAR2 bulk entry.Specifies the first friction coefficient when the Tangential Stiffness Selection list is set to Friction Depends on Sliding Velocity or Friction Depends on a Linear Law of the Sliding Velocity.
Friction Coefficient 2	FPARA2 parameter of the BCTPAR2 bulk entry.Specifies the second friction coefficient when the Tangential Stiffness Selection list is set to Friction Depends on Sliding Velocity or Friction Depends on a Linear Law of the Sliding Velocity.
Critical Sliding Velocity	VCRIT parameter of the BCTPAR2 bulk entry.Specifies the critical sliding velocity when the Tangential Stiffness Selection list is set to Friction Depends on Sliding Velocity or Friction Depends on a Linear Law of the Sliding Velocity.
Friction Coefficient vs Sliding Velocity	CFVE parameter of the BCTPAR2 bulk entry.Lets you specify a table-based field that defines the friction coefficient as function of sliding velocity when Tangential Stiffness Selection is set to Friction Depends on Time, Velocity or Temperature.
Friction Coefficient vs Time	CFNF parameter of the BCTPAR2 bulk entry.Lets you specify a table-based field that defines the friction coefficient as function of time when Tangential Stiffness Selection is set to Friction Depends on Time, Velocity or Temperature.
Friction Coefficient vs Temperature	CFTE parameter of the BCTPAR2 bulk entry.Lets you specify a table-based field that defines the friction coefficient as function of temperature when Tangential Stiffness Selection is set to Friction Depends on Time, Velocity or Temperature.
Critical Slip	SCRIT parameter of the BCTPAR2 bulk entry.Defines the critical
Delay Friction	FRICDLY field in the BCTPARA bulk data entry.Specifies whether to delay the application of friction is delayed (whether friction is applied on a node in the time step after the node comes into contact). Delaying the application of friction may improve the convergence of the solution.

Displacement

Displacement Scaling Option	DISCAL field in the BCTPARM bulk data entry.Controls whether the software scales the displacement.When this option is set to Scale as Required, incremental displacements are scaled to limit the penetrations to less than the Displacement Scaling Tolerance value.
Displacement Scaling Tolerance	DISTOL field in the BCTPARM bulk data entry.Lets you specify the displacement scaling tolerance.

Sliding

Sliding Formulation	DISP field in the BCTPARM bulk data entry.Selects the sliding contact formulation.
Contact Geometry Update Occurrence	GUPDATE field in the BCTPARM bulk data entry.Controls whether the contact geometry updates during the analysis.
Geometry Update Tolerance	GUPTOL field in the BCTPARM bulk data entry.Lets you specify the geometry update tolerance. If the relative sliding distance between the source and target regions exceeds this tolerance, the software initiates a geometry update with large displacement

Convergence

Contact Convergence Criteria	CNTCONV field in the BCTPARM bulk data entry.Specifies whether the contact convergence criteria is based on the Contact Penetration Tolerance or Contact Augmentation Traction Convergence value.
Contact Penetration Tolerance	PTOL field in the BCTPARM bulk data entry.Specifies the contact penetration tolerance value. If the contact penetrations exceed this tolerance, the software performs an extra augmentation loop. If the penetrations are below this tolerance, the software considers the augmentation loop to be converged. Additionally, if the global solution convergence criteria is satisfied, then the software considers the time step converged.
Contact Augmentation Traction Convergence	CTOL field in the BCTPARM bulk data entry.Specifies the contact augmentation tolerance value when Contact Convergence Criteria is set to CTOL.
Iterative Contact Force Convergence	RCTOL field in the BCTPARM bulk data entry.Specifies the convergence value for iterative contact forces.
Max Iterations Status Loop	MAXS field in the BCTPARM bulk data entry.Specifies the maximum number of iterations of the outer or status loop. The outer loop determines which contact locations (or contact elements) are active.
Max Iterations Force Loop	MAXF field in the BCTPARM bulk data entry.Specifies the maximum number of iterations of the inner or force loop. The contact algorithm iterates in two nested loops: an inner and an outer loop. The inner loop forces a condition of zero penetration between the contacting bodies. For more information, see Global Solution Strategy in the Simcenter Nastran User’s Guide.
Allowable Number of Contact Changes	NCHG field in the BCTPARM bulk data entry.Lets you specify the permitted number of contact changes as a real number.
Fraction of Active Contact Elements	NCHG field in the BCTPARM bulk data entry.Lets you specify the permitted number of contact changes as a fraction of the number of active contact elements in each outer loop of the contact algorithm. The software evaluates the number of active contact elements at each outer loop iteration.
All Contact Elements Can Become Inactive	CSTRAT field in the BCTPARM bulk data entry.Controls whether all the contact elements can become inactive. Under certain conditions, all of the contact elements could become inactive, which may lead to singularities. Setting this parameter to No reduces the likelihood of all contact elements becoming inactive.

Stabilization

Stabilization Damping	CTDAMP field in the NXSTRAT bulk data entry.Requests the stabilization damping option when you are relying on the contact condition to prevent rigid body conditions, but the contact condition is not active.
Normal Stabilization Damping Coefficient	CTDAMPN field in the NXSTRAT bulk data entry.If the Stabilization Damping list is set to any option other than None, use this option to either scale the normal damping value, which the software computes automatically, or to define the normal damping value explicitly.
Tangential Stabilization Damping Coefficient	CTDAMPT field in the NXSTRAT bulk data entry.If the Stabilization Damping list is set to any option other than None,use this option to either scale the tangential damping value ,which the software computes automatically, or to define the normal damping value explicitly.
Open Gap Tolerance Scale Factor	OPNTOL field in the BCTPARM bulk data entry.Lets you specify the open gap tolerance scale factor.
No Separation Contact Option	NOSEP field in the BCTPARM bulk data entry.Controls whether the software computes open contact stiffness.Use Open Contact StiffnessWhen contact stiffness is recomputed in a consecutive nonlinear iteration, contact elements that are inactive as a result of normal tractions=0.0 and no penetration, and which have a gap greater than 0.0 remain inactive in the consecutive iteration. Use OPNSTF and OPNTOLThe software applies the open contact stiffness (Open Contact Stiffness Scale Factor value * closed stiffness) to the inactive contact elements that have a gap value less than or equal to Open Contact Stiffness Scale Factor * characteristic length, but greater or equal than 0.0. The contact elements with a gap greater than Open Contact Stiffness Scale Factor * characteristic length remain inactive. While sliding is permitted with this option, the magnitude of the sliding can be controlled by the tangential penalty factor. To define frictionless sliding, set the coefficient of friction=0.0 or Tangential Penalty Scale Factor=0.0.

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Defining parameters for contact conditions (Simcenter Nastran)

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Contact Parameters–Global Pair dialog box, Simcenter 3D 2021.1 Series

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