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 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.

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