Secondary and main surfaces

By default, contact pairs in Abaqus/Standard use a pure main-secondary contact algorithm: nodes on one surface (the secondary surface) cannot penetrate the segments that make up the other surface (the main surface), as shown in Figure 1. The algorithm places no restrictions on the main surface; it can penetrate the secondary surface between secondary nodes, as shown in Figure 1.

Figure 1. The main surface can penetrate the secondary surface.

Due to the strict main-secondary formulation, you must be careful to select the secondary and main surfaces correctly in order to achieve the best possible contact simulation. Some simple rules to follow are:

  • the secondary surface should be the more finely meshed surface; and

  • if the mesh densities are similar, the secondary surface should be the surface with the softer underlying material.

The general contact algorithm in Abaqus/Standard enforces contact in an average sense between interacting surfaces; Abaqus/Standard automatically assigns main and secondary roles.