Contact Module

Theory

Mechanical contact between two deformable bodies is based on three requirements.

That is, the penetration distance (typically referred to as the gap in the contact literature) of one of the body into another must not be positive; the contact force opposing penetration must be positive in the normal direction; and either the penetration distance or the contact force must be zero at all times. In the MOOSE Contact Module, these contact constraints are enforced through the use of either node/face constraints or by using a mortar method.

Node/Face Mechanical Contact

Contact constraints can be enforced through the use of node/face constraints in a manner similar to that detailed by Heinstein and Laursen (1999)). In this approach, first, a geometric search determines which secondary nodes have penetrated primary faces. For those nodes, the internal force computed by the divergence of stress is moved to the appropriate primary face at the point of contact. Those forces are distributed to primary nodes by employing the finite element shape functions. Additionally, the secondary nodes are constrained to remain on the primary faces, preventing penetration. The module currently supports frictionless, frictional, and glued contact.

Mortar-Based Mechanical Contact

Models specific for mechanical contact enforcement have been developed based on the MOOSE mortar constraint system, and provide an alternative discretization technique for solving mechanical contact. Results of performance studies using this approach are summarized in MortarPerformance.

Contact Syntax Block

Setting up a model to use contact enforcement in MOOSE requires the creation of multiple types of MOOSE objects. Using the top-level Contact syntax block, which streamlines the process of setting up these objects, is highly recommended, and supports most available types of contact. The following input file example shows the basic usage of the Contact block:

[Contact]
  [./leftright]
    secondary = 3
    primary = 2
    model = frictionless
    penalty = 1e+6
    normal_smoothing_distance = 0.1
  [../]
[]

Objects, Actions, and Syntax

• Contact App
• ContactPressureAuxComputes the contact pressure from the contact force and nodal area
• MortarArchardsLawAuxReturns the weighted gap velocity at a node. This quantity is useful for mortar contact, particularly when dual basis functions are used in contact mechanics
• MortarFrictionalPressureVectorAuxThis class creates an auxiliary vector for outputting the mortar frictional pressure vector.
• MortarFrictionalStateAuxThis class creates discrete states for nodes into frictional contact, including contact/no-contact and stick/slip.
• WeightedGapVelAuxReturns the weighted gap velocity at a node. This quantity is useful for mortar contact, particularly when dual basis functions are used in contact mechanics

• Contact App
• ComputeDynamicFrictionalForceLMMechanicalContactComputes the tangential frictional forces for dynamic simulations
• ComputeDynamicWeightedGapLMMechanicalContactComputes the normal contact mortar constraints for dynamic simulations
• ComputeFrictionalForceLMMechanicalContactComputes the tangential frictional forces
• ComputeWeightedGapLMMechanicalContactComputes the weighted gap that will later be used to enforce the zero-penetration mechanical contact conditions
• MechanicalContactConstraintApply non-penetration constraints on the mechanical deformation using a node on face, primary/secondary algorithm, and multiple options for the physical behavior on the interface and the mathematical formulation for constraint enforcement
• NormalMortarLMMechanicalContactEnforces the normal contact complementarity conditions in a mortar discretization
• NormalMortarMechanicalContactThis class is used to apply normal contact forces using lagrange multipliers
• NormalNodalLMMechanicalContactImplements the KKT conditions for normal contact using an NCP function. Requires that either the gap distance or the normal contact pressure (represented by the value of variable) is zero. The LM variable must be of the same order as the mesh
• NormalNodalMechanicalContactApplies the normal contact force to displacement residuals through a Lagrange Multiplier
• RANFSNormalMechanicalContactApplies 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
• TangentialMortarLMMechanicalContactEnsures that the Karush-Kuhn-Tucker conditions of Coulomb frictional contact are satisfied
• TangentialMortarMechanicalContactUsed to apply tangential stresses from frictional contact using lagrange multipliers
• TangentialNodalLMMechanicalContactImplements the KKT conditions for frictional Coulomb contact using an NCP function. Requires that either the relative tangential velocity is zero or the tangential stress is equal to the friction coefficient times the normal contact pressure.

• Contact App
• ContactActionSets up all objects needed for mechanical contact enforcement

• Contact App
• ContactSlipDamperDamp the iterative solution to minimize oscillations in frictional contact constriants between nonlinear iterations

• Contact App
• ContactDOFSetSizeOutputs the number of dofs greater than a tolerance threshold indicating mechanical contact

• Contact App
• ContactSplitSplit-based preconditioner that partitions the domain into DOFs directly involved in contact (on contact surfaces) and those that are not

• Contact App
• AugmentedLagrangianContactProblemManages nested solution for augmented Lagrange contact

• Contact App
• NodalAreaCompute the tributary area for nodes on a surface

References