This option is used to provide additional optional solution controls for models involving contact between bodies. The standard solution controls are usually sufficient, but additional controls are helpful to obtain cost-effective solutions for models involving complicated geometries and numerous contact interfaces, as well as for models in which rigid body motions are initially not constrained.
The *CONTACT CONTROLS option can be repeated to set different control values for different contact pairs. It must be used in conjunction with the *CONTACT PAIR option in ABAQUS/Explicit analyses.
Products: ABAQUS/Standard ABAQUS/Explicit
Type: History data
Level: Step
Warning: The parameters LAGRANGE MULTIPLIER, MAXCHP, PERRMX, SLIDE DISTANCE, and UERRMX are intended for experienced analysts and should be used with care.
Set this parameter equal to the allowable penetration. Only contact constraints defined with augmented Lagrangian surface behavior will be affected by this parameter.
Set this parameter equal to the ratio of the allowable penetration to the characteristic contact surface face dimension. Only contact constraints defined with augmented Lagrangian surface behavior will be affected by this parameter. By default, the RELATIVE PENETRATION TOLERANCE parameter is set to 0.1% except for finite-sliding, surface-to-surface contact, in which case the default setting is 5%.
Include this parameter to automatically address situations where an initial rigid body mode exists normal to the contact direction. This option activates viscous damping in the normal direction to prevent numerical difficulties associated with rigid body motion that occurs when surfaces not initially in contact are brought into contact. The bodies should be moved into contact in a single step, but there should not be significant further deformation of the parts during the step due to the loads bringing them into contact. This parameter must be used in conjunction with the SLAVE and MASTER parameters to specify a contact pair. For more general situations in which rigid body modes need to be controlled, use the STABILIZE parameter instead.
Include this parameter to have ABAQUS/Standard automatically compute an overclosure tolerance and a separation pressure tolerance to prevent chattering in contact. This parameter cannot be used with the MAXCHP, PERRMX, and UERRMX parameters.
Set FRICTION ONSET=IMMEDIATE (default) to include friction in the increment when contact occurs. Set FRICTION ONSET=DELAYED to delay the application of friction to the increment after contact occurs.
Set LAGRANGE MULTIPLIER=YES to enforce the contact constraints with Lagrange multipliers.
Set LAGRANGE MULTIPLIER=NO to enforce the constraints without Lagrange multipliers. Setting LAGRANGE MULTIPLIER=NO is not recommended for problems with a high stiffness since it may lead to numerical problems during equation solution (such as singularities). For the default direct enforcement of hard contact LAGRANGE MULTIPLIER=NO is not allowed.
The value of the contact stiffness determines whether or not Lagrange multipliers are used by default. When the default penalty stiffness settings are used for penalty or augmented Lagrange contact, Lagrange multipliers are not used by default. If the penalty stiffness used in penalty or augmented Lagrange contact is set to greater than 1000 times the representative underlying element stiffness, Lagrange multipliers are used by default. For softened contact using the direct enforcement method (see “Contact pressure-overclosure relationships,” Section 30.1.2 of the ABAQUS Analysis User's Manual), Lagrange multipliers are used by default only if the maximum slope of the pressure-overclosure relationship exceeds 1000 times the representative underlying element stiffness.
Set this parameter equal to the master surface name to apply the controls to a specific contact pair. This parameter must be used in conjunction with the SLAVE parameter to specify a contact pair.
Set this parameter equal to the maximum number of points that are permitted to violate contact conditions in any increment. The amount by which the condition can be violated is limited by the PERRMX and UERRMX parameters, at least one of which must be used in conjunction with this parameter. If more than this number of points violate the contact conditions, the solution will not be accepted.
Set this parameter equal to the maximum value of tensile stress (tensile force in GAP- or ITT-type contact elements) allowed to be transmitted at a contact point. If any point in contact has a tensile stress/force across the contact interface greater than PERRMX, iteration will occur regardless of the value of MAXCHP (which must be used in conjunction with this parameter). By default, no tensile stress can be transmitted.
Include this parameter to reset all contact controls to their default values. This parameter cannot be used with any other parameters, except for the SLAVE and MASTER parameters. When this parameter is used in conjunction with the SLAVE and MASTER parameters, the controls applied to the specific contact pair are removed.
Set this parameter equal to the slave surface name to apply the controls to a specific contact pair. This parameter must be used in conjunction with the MASTER parameter to specify a contact pair.
This parameter is relevant only for finite-sliding simulations with three-dimensional deformable master surfaces when the “contact patch” algorithm is used instead of the “active topology” algorithm to account for changes in contact connectivity. In these cases ABAQUS will choose a default contact patch size, but setting this parameter equal to the maximum distance that slave nodes can slide on the master surface can sometimes improve analysis performance.
This parameter must be used in conjunction with the SLAVE and MASTER parameters to specify a contact pair. Setting the SLIDE DISTANCE parameter to zero will revert back to the default contact patch size if the contact patch algorithm is in effect. See “Efficiently accounting for changes in contact connectivity in the equation solver” in “Adjusting contact controls in ABAQUS/Standard,” Section 29.2.12 of the ABAQUS Analysis User's Manual for more information.
Include this parameter to address situations where rigid body modes exist as long as contact is not fully established. This parameter activates damping in the normal and tangential directions based on the stiffness of the underlying mesh and the time step size. If no value is assigned to this parameter, ABAQUS will calculate the damping coefficient automatically. If a value is assigned to this parameter, ABAQUS will multiply the automatically calculated damping coefficient by this value. If the damping coefficient is defined directly on the data line, any value assigned to this parameter will be ignored.
The STABILIZE parameter can be used to specify damping for the whole model or for an individual contact pair by using the SLAVE and MASTER parameters. Values specified for a specific contact pair override the values for the whole model, if given.
Set this parameter equal to the factor by which ABAQUS/Standard will scale the default penalty stiffness to obtain the stiffnesses used for the contact pairs. Only contact constraints enforced with the augmented Lagrangian and penalty methods will be affected by this parameter. This scale factor acts as an additional multiplier on any scale factor specified on the data line of the *SURFACE BEHAVIOR option.
Set this parameter equal to a fraction of the damping in the normal direction as specified with the STABILIZE parameter. By default, the tangential and normal stabilization are the same.
Set this parameter equal to the maximum overclosure distance allowed at a slave node that is considered to be open. If any contact point violates the contact constraint by more than UERRMX, iteration will occur regardless of the value of MAXCHP (which must be used in conjunction with this parameter). By default, no overclosure is allowed.
First (and only) line:
Damping coefficient to be used in the contact interface. The value entered overrides the damping coefficient calculated by ABAQUS. When a nonzero value is entered, the value assigned to the STABILIZE parameter is ignored.
Fraction of the damping that remains at the end of the step. The default is zero. Set to one to keep the damping constant over the step. If a nonzero value is specified, convergence problems may occur in a subsequent step if stabilization is not used in that step.
Clearance at which the damping becomes zero. By default, the clearance is calculated by ABAQUS based on the facet size associated with the contact pair. Set to a large value to obtain damping independent of the opening distance.
Warning: These controls are intended for experienced analysts and should be used with care. Using nondefault values of these controls may greatly increase the computational time of the analysis or produce inaccurate results.
Set this parameter equal to the name of the contact pair set associated with this contact controls definition. The contact controls defined with this option will be applied to all contact pairs having this contact pair set name.
Set FASTLOCALTRK=NO if contact is not being enforced appropriately. A more conservative local tracking method will be used that may resolve the error. The default is FASTLOCALTRK=YES, which uses a more computationally efficient local tracking method (see “Defining contact pairs in ABAQUS/Explicit,” Section 29.4.1 of the ABAQUS Analysis User's Manual).
Set this parameter equal to the maximum number of increments between global contact searches. The default is 100 increments for two-surface contact and 4 increments for self-contact (see “Defining contact pairs in ABAQUS/Explicit,” Section 29.4.1 of the ABAQUS Analysis User's Manual).
Include this parameter to reset all of the optional controls to their default values. Those controls that are explicitly specified with other parameters on the same *CONTACT CONTROLS option are not reset. If this parameter is omitted, only the explicitly specified controls will be changed in the current step; the others will remain at their previous settings.
Set this parameter equal to the factor by which ABAQUS/Explicit will scale the default penalty stiffnesses to obtain the stiffnesses used for the penalty contact pairs within the contact pair set specified with the CPSET parameter. Penalty contact constraints defined with softened surface behavior and kinematic contact constraints will not be affected by this parameter. By default, the SCALE PENALTY parameter is set to unity.
Set this parameter equal to the number of increments between checks for highly warped facets on master surfaces. By default, this check is performed every 20 increments. More frequent checks will cause a slight increase in computational time (see “Common difficulties associated with contact modeling using the contact pair algorithm in ABAQUS/Explicit,” Section 29.4.6 of the ABAQUS Analysis User's Manual).
Set this parameter equal to the out-of-plane warping angle, measured in degrees, at which a facet will be considered to be highly warped. The out-of-plane warping angle is defined as the amount of variation of the surface normal over a facet. The default is WARP CUT OFF=20 (see “Common difficulties associated with contact modeling using the contact pair algorithm in ABAQUS/Explicit,” Section 29.4.6 of the ABAQUS Analysis User's Manual).