About General Contact

General contact is a global interaction property that defines the default behavior for contacting surfaces throughout your model.

This page discusses:

Typically, general contact interactions apply to all exterior faces and feature edges of the model. If applicable, you can include analytical rigid surfaces, edges based on beams and trusses, and Eulerian material boundaries. You can also include or exclude specific surface pairs from the general contact domain.

An analysis can include general contact interactions and surface-to-surface (or self-contact) interactions. However, only one general contact interaction can be active in a step during an analysis, and you cannot specify general contact (including self-contact) between two analytical rigid surfaces.

When you define general contact, the app creates a contact initialization feature and assignment automatically. You can delete the feature or the assignment, but doing so renders the general contact definition invalid.

One use of general contact is to define contact between Lagrangian bodies and Eulerian materials in a coupled Eulerian-Lagrangian analysis.

Contact Smoothing

The app uses a CAD-based algorithm to smooth any contacting surfaces and to improve the accuracy and robustness of the simulation. Smoothing can reduce stress noise and contact pressure noise in the results, providing a more uniform and accurate solution.

For simulations involving small deformation, smoothing is most beneficial when the discretized mesh is coarse and contains first-order elements in the contact region; however, significant benefits are common even when the mesh is quite refined or contains higher-order elements.

For simulations involving large deformation, smoothing often has an insignificant effect if the geometry-correction distances are small compared to the element dimensions. However, smoothing can degrade the solution accuracy in some cases.

The effectiveness of surface-to-surface contact smoothing does not degrade when there is relative motion between the contacting surfaces; for example, the smoothing technique works well for cases involving large sliding contact but small deformation.

Smoothing contacting surfaces does not overcome all robustness and accuracy issues associated with a coarse mesh. For example, resolving complex stress variations requires adequate mesh refinement. Use of extremely coarse meshes at curved contact interfaces still tends to degrade simulation robustness.

Contact Stabilization

Applying stabilization in general contact can help you 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. Contact stabilization helps control rigid body motion in static problems before contact closure and friction restrain the motion. Using stabilization activates damping in the normal and tangential directions based on the stiffness of the underlying mesh and the time step size.