Contact Action

Description

ContactAction is a MOOSE action that constructs objects needed for mechanical contact enforcement. This is invoked by including the Contact block at the top level in a MOOSE input file. See the page documenting the syntax for that block for a description, example usage, and parameters.

For the mortar and mortar_penalty formulations, ContactAction forwards "mortar_3d_qp_mapping" to its generated mortar constraints and user objects. See Quadrature Point Mapping for the two mapping methods. The parameter has no effect in 2D, and every mortar consumer on the same primary-secondary boundary pair must use the same mapping mode.

For the mortar Lagrange-multiplier contact formulation, "lm_space" controls the finite element space used for mortar Lagrange multiplier variables generated by ContactAction. The MATCH_DISPLACEMENT option gives these generated mortar variables the same order as the displacement variables. The LINEAR option creates first-order LAGRANGE generated mortar variables even when the displacement variables are higher order. This option only affects variables created by ContactAction; users who define mortar constraints manually still choose the Lagrange multiplier family and order directly in [Variables].

Lower-order contact multiplier interpolations are a standard option for mortar contact with quadratic surface discretizations. Puso, Laursen, and Solberg discuss alternative multiplier interpolations for quadratic-element mortar contact and show that corner-node/linear contact pressure fields can avoid inconsistencies that arise with quadratic contact pressure interpolations while retaining good convergence Puso et al. (2008).

For node-to-segment mechanical contact, the action offers the possibility to automatically set up mechanical contact pairs given a maximum distance between contacting boundary centroids. To use that option, the user must set automatic_pairing_method = CENTROID. The user can leverage this capability by providing automatic_pairing_distance and automatic_pairing_boundaries. This is particularly useful when many feasible contact interactions can take place in a periodically repeating pattern.

Alternatively, also for node-to-segment, the user can choose to select a computation of proximity based on nodal locations. In essence, for all boundaries provided by the user in automatic_pairing_boundaries, the action will search for all nodes whose distance is less than automatic_pairing_distance. If so, each nodal pair distance from different boundaries less than the automatic_pairing_distance distance will create a contact pair. Repeated contact pairs are automatically eliminated. In order to activate this feature, in addition to automatic_pairing_boundaries and automatic_pairing_distance, the user needs to set the input parameter automatic_pairing_method = NODE.

References

References