# About contact pairs in Abaqus/Explicit

 Abaqus/Explicit provides two algorithms for modeling contact and interaction problems: the general contact algorithm and the contact pair algorithm. See About contact interactions for a comparison of the two algorithms. This section describes how to define contact pairs with surfaces for contact simulations in Abaqus/Explicit. Contact pairs in Abaqus/Explicit: are part of the history definition of the model and can be created, modified, and removed from step to step (unlike Abaqus/Standard, where contact pairs are model data); use sophisticated tracking algorithms to ensure that proper contact conditions are enforced efficiently; can be used simultaneously with the general contact algorithm (i.e., some interactions can be modeled with contact pairs, while others are modeled with the general contact algorithm); can be formed using a pair of rigid or deformable surfaces or a single deformable surface; do not have to use surfaces with matching meshes; cannot be formed with one two-dimensional surface and one three-dimensional surface; and cannot be used for self-contact where the surface is composed of both first-order elements and second-order elements. The following topics are discussed:
 Related Topics About contact interactions In Other Guides Element-based surface definition Node-based surface definition Analytical rigid surface definition *CONTACT CONTROLS *CONTACT PAIR *SURFACE Defining surface-to-surface contact Defining self-contact

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