Finite elements and rigid bodies are the fundamental components of an ABAQUS model. Finite elements are deformable, whereas rigid bodies move through space without changing shape. While users of finite element analysis programs tend to have some understanding of what finite elements are, the general concept of rigid bodies within a finite element program may be somewhat new.

For computational efficiency ABAQUS has a general rigid body capability. Any body or part of a body can be defined as a rigid body; most element types can be used in a rigid body definition (the exceptions are listed in “Rigid body definition,” Section 2.4.1 of the ABAQUS Analysis User's Manual). The advantage of rigid bodies over deformable bodies is that the motion of a rigid body is described completely by no more than six degrees of freedom at a reference node. In contrast, deformable elements have many degrees of freedom and require expensive element calculations to determine the deformations. When such deformations are negligible or not of interest, modeling a component as a rigid body produces significant computational savings without affecting the overall results.