PCONT

Format

Examples

Definitions

Comments

1. The initial contact gap opening is calculated automatically based on the relative location of secondary and main nodes (in the original, undeformed mesh). To account for additional material layers covering main and secondary objects, the GPAD entry can be used. GPAD option THICK automatically accounts for shell thickness on both sides of the contact interface (this also includes the effects of shell element offset ZOFFS or composite offset Z0), when the main and/or secondary are shell surfaces (SET of shell element types or SURF of shell element faces). The THICK option will only apply automatic padding if shells are selected for main/secondary in the contact interface (for example, padding is not applied for "skinned" solid elements that are selected as a main/secondary in the contact interface). For further information, refer to Contact Interface Padding (GPAD) in the User Guide.
2. Option STIFF=AUTO determines the value of normal stiffness for each contact element using the stiffness of surrounding elements. Additional options SOFT and HARD create respectively softer or harder penalties. SOFT can be used in cases of convergence difficulties and HARD can be used if undesirable penetration is detected in the solution. A negative value for STIFF indicates that a stiffness scaling factor equal to |Real < 0.0| is defined. This scaling is applied on the stiffness value via STIFF = AUTO. For further information, refer to Penalty-based Contact in the User Guide.

   Optional continuation lines STFEXP and STFQDR are available for the definition of exponential and quadratic penalties. These penalties do not apply to FREEZE contact, they are also ignored for contacts in linear analysis.

   For further information, refer to Linear Penalty Curve (Nonlinear Analysis) and Nonlinear Penalty Curve (Nonlinear Analysis) in the User Guide.

3. MU1=STICK is interpreted in OptiStruct as an enforced stick condition - such contact interfaces will not enter the sliding phase. Of course, the enforced stick only applies to contacts that are closed.
   Note: In order to effectively enforce the stick condition, frictional offset may need to be turned off. For further information, refer to Friction in the User Guide.

   MU1=FREEZE enforces zero relative motion on the contact surface - the contact gap opening remains fixed at the original value and the sliding distance is zero. Also, rotations at the secondary node are matched to the rotations of the main patch. The FREEZE condition applies to all respective contact elements, no matter whether open or closed. Also, this condition is effective irrespective of the frictional offset setting.

   MU1 set to an integer value references a TABLES1 or TABLEG ID. TABLES1 or TABLEG entries (xi,yi) correspond to pseudo time-friction coefficient values. For nonlinear subcases, table lookup is performed to compute a value for the coefficient of friction based on the pseudo-time value of the current increment. An error message is issued and OptiStruct will stop, if a negative value is returned. If a zero value is returned, the CONTACT that refers to the PCONT entry will be treated as frictionless. For linear subcases, the friction coefficient at pseudo-time zero will be used. MU2 will be ignored, if MU1 is provided as TABLES1 or TABLEG ID.

   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, refer to Friction in the User Guide.

4. TABLES1 or TABLEG entries can be used to define the contact pressure-overclosure relationship, as outlined below.

   Field	Data	Comments
   x – values	Overclosure values	The values must be in ascending order. The values can be negative and will refer to gap opening values in this case.
   y – values	Pressure values	The values must be in ascending order. The values must be positive.

   Under the above conditions, the slope of the pressure-overclosure curve (penalty) will not be negative or zero.

5. For more information on clearance, refer to Contact Interface Parameters (Contact Control) in the User Guide.
6. 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.
7. CONTPRM, KTLIN can be used to control the tangential stiffness KT for closed contact in linear analysis when STIFF = Real > 0.0 and MU1 = Real > 0.0 on the PCONT entry referenced by the contact.
8. CLRNC ID can be specified on the CLEARANCE field in the CONTACT or PCONT Bulk Data Entry. If there is a conflict, then the CLRNC ID specified for PCONT takes precedence.
9. The augmented Lagrange multiplier method is applicable to Nonlinear Static and Nonlinear Transient Analysis except when combined with the following features:
   • FREEZE/TIE contact
   • CGAP/CGAPG core N2S contact
   • Nonlinear penalty or the adaptive penalty method
   • The arc-length method
   For more information, refer to Augmented Lagrange Multiplier (ALM) Method (Nonlinear Analysis) in the User Guide.
10. If the penetration of a secondary node on the main surface exceeds the specified tolerance, additional augmentation iterations are performed. For no-separation contact, the penetration tolerance is effective for both the penetration and the opening distance once it is closed.
11. The default penetration tolerance is defined relative to the average characteristic edge length, L, of the contact interface as follows:

    TRACK

    Tolerance

    SMALL(SMDISP)

    L*0.1%*w

    SMALL(LGDISP)

    L*1%*w

    FINITE/CONSLI

    L*5%*w

    Where, $w=\frac{1}{\sqrt{0.1\left|SFKN\right|}}$ is an additional scaling factor effective for -10.0≤SFKN≤0.0. This scaling also applies to SFKN=AUTO or SOFT, and for SFKN≤10.0, or SFKN>0.0, w = 1.0.
12. The penalty stiffness employed by the augmented Lagrange multiplier method is independent of the STIFF field. Option SFKN=AUTO determines the value of the normal penalty stiffness for each contact element using the stiffness of surrounding elements along the normal direction of the surface. Additional options AUTO, HARD, SOFT or Real<0.0 are available as a scaling factor applied on the stiffness value via SFKN=AUTO.
13. This card is represented as a property in HyperMesh.