# RANFSNormalMechanicalContact

Enforces the zero penetration constraint using the Reduced Active Nonlinear Function Set (RANFS) scheme. The algorithm is as follows: do a min comparison between the penetration and the Lagrange Multiplier (LM) associated with the zero penetration constraint. If the penetration (properly signed) is less than the LM, then we replace the non-linear residual equation for the secondary node with the zero-penetration constraint equation (represented simply by the gap). In this way the gap is required to be zero.

• No Lagrange Multipliers, e.g. no saddle-point and consequently we are free to use preconditioners like AMG

• No penalty term, so no introduction of ill conditioning into the matrix

• Exact satisfaction of the constraints

The RANFSNormalMechanicalContact object includes ping-ponging protection. It detects when a secondary node has alternated back and forth between two different element faces a sufficient number of times (currently face1-face2-face1-face2-face1) and then fixes the issue by applying more RANFS Explicitly, we apply a number of equality constraints equal to the mesh dimension tying together the locations of the secondary node and the nearest primary node (which we assert is a node that both primary faces involved in the ping-pong share). This ping-ponging protection is necessary for solving step 19 of the full-bouncing-block-ranfs test. Without the protection the solve does not converge and the time-step gets cut.

Applies the Reduced Active Nonlinear Function Set scheme in which the secondary node's non-linear residual function is replaced by the zero penetration constraint equation when the constraint is active

## Input Parameters

• componentThe force component constraint that this object is supplying

C++ Type:MooseEnum

Options:x y z

Description:The force component constraint that this object is supplying

• displacementsThe displacements appropriate for the simulation geometry and coordinate system

C++ Type:std::vector

Options:

Description:The displacements appropriate for the simulation geometry and coordinate system

• variableThe name of the variable that this constraint is applied to.

C++ Type:NonlinearVariableName

Options:

Description:The name of the variable that this constraint is applied to.

### Required Parameters

• execute_onLINEARThe list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM.

Default:LINEAR

C++ Type:ExecFlagEnum

Options:NONE INITIAL LINEAR NONLINEAR TIMESTEP_END TIMESTEP_BEGIN FINAL CUSTOM

Description:The list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM.

• normal_smoothing_distanceDistance from edge in parametric coordinates over which to smooth contact normal

C++ Type:double

Options:

Description:Distance from edge in parametric coordinates over which to smooth contact normal

• normal_smoothing_methodMethod to use to smooth normals (edge_based|nodal_normal_based)

C++ Type:std::string

Options:

Description:Method to use to smooth normals (edge_based|nodal_normal_based)

• orderFIRSTThe finite element order used for projections

Default:FIRST

C++ Type:MooseEnum

Options:FIRST SECOND THIRD FOURTH

Description:The finite element order used for projections

• ping_pong_protectionFalseWhether to protect against ping-ponging, e.g. the oscillation of the secondary node between two different primary faces, by tying the secondary node to the edge between the involved primary faces

Default:False

C++ Type:bool

Options:

Description:Whether to protect against ping-ponging, e.g. the oscillation of the secondary node between two different primary faces, by tying the secondary node to the edge between the involved primary faces

• primaryThe boundary ID associated with the primary side

C++ Type:BoundaryName

Options:

Description:The boundary ID associated with the primary side

• primary_variableThe variable on the primary side of the domain

C++ Type:std::vector

Options:

Description:The variable on the primary side of the domain

• secondaryThe boundary ID associated with the secondary side

C++ Type:BoundaryName

Options:

Description:The boundary ID associated with the secondary side

• tangential_toleranceTangential distance to extend edges of contact surfaces

C++ Type:double

Options:

Description:Tangential distance to extend edges of contact surfaces

### Optional Parameters

• control_tagsAdds user-defined labels for accessing object parameters via control logic.

C++ Type:std::vector

Options:

Description:Adds user-defined labels for accessing object parameters via control logic.

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Options:

Description:Set the enabled status of the MooseObject.

• use_displaced_meshTrueWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Default:True

C++ Type:bool

Options:

Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

• extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

C++ Type:std::vector

Options:

Description:The extra tags for the matrices this Kernel should fill

• extra_vector_tagsThe extra tags for the vectors this Kernel should fill

C++ Type:std::vector

Options:

Description:The extra tags for the vectors this Kernel should fill

• matrix_tagssystemThe tag for the matrices this Kernel should fill

Default:system

C++ Type:MultiMooseEnum

Options:nontime system

Description:The tag for the matrices this Kernel should fill

• vector_tagsnontimeThe tag for the vectors this Kernel should fill

Default:nontime

C++ Type:MultiMooseEnum

Options:nontime time

Description:The tag for the vectors this Kernel should fill