ABAQUS/Explicit provides two algorithms for modeling contact. General contact interactions allow you to define contact between many or all regions of a model with a single interaction. The surfaces that can interact with one another are considered the contact domain and can span many disconnected regions of a model. Contact pair interactions describe contact between two deformable surfaces, a deformable surface and a rigid surface, a deformable surface and itself, or a set of nodes and a deformable or rigid surface. Although the general contact algorithm is more powerful and allows for simpler contact definitions, the contact pair algorithm must be used in certain cases where more specialized contact features are desired. The two contact algorithms can be used together in the same analysis. Refer to Contact interaction analysis: overview, Section 29.1.1 of the ABAQUS Analysis User's Manual, for a detailed discussion and comparison of the ABAQUS/Explicit contact algorithms.
An ABAQUS/Explicit contact simulation is usually defined simply by specifying the contact algorithm to use and the surfaces that will interact with one another. In some cases where the default contact settings are not appropriate, other aspects of the contact simulation can be specified; for example, a mechanical interaction model that considers friction.