Rigid Parts
A rigid part can displace under the loading, but only as a rigid body, i.e. without deformation or strain.
Rigid parts are computationally inexpensive, therefore, can be used to simplify the analysis model and reduce the analysis runtime.
A typical application for rigid parts is modeling of relatively stiff parts in the assembly, for example, steel fasteners connecting plastic parts.
Designating a part as rigid discards the material properties previously assigned to the part, if any.