When you define a body's Stiffness Behavior as , you are telling to the application to not allow the body to deform during the solution process. This feature is useful if a mechanism has only rigid body motion or, if in an assembly, only some of the parts experience most of the strains. It is also useful if you are not concerned about the stress/strain of that component and wish to reduce CPU requirements during meshing or solve operations.
The application does not mesh a rigid body and the solver represents the body as a single mass element. However, the system maintains the mass element's mass and inertial properties. The Mass, Centroid, and Moments Of Inertia properties for the body are available in the Details view of the body object.
The following restrictions apply to rigid bodies:
Rigid bodies are only valid in Static Structural, Transient Structural, Harmonic Response, Modal, Rigid Dynamics, Random Vibration, and Response Spectrum analyses for the objects listed below. Animated results are available for all analysis types except a Modal analysis.
Point Mass
Joint
Spring
Remote Displacement
Remote Force
Moment
Contact
Rigid bodies are valid when scoped to solid bodies, surface bodies, or line bodies in an Explicit Dynamics analysis for the following objects:
Fixed Support
Displacement
Velocity
Spring
Remote Displacement
The following outputs are available for rigid bodies, and are reported at the centroid of the rigid body:
Results: Displacement, Velocity, and Acceleration.
Probes: Deformation, Position, Rotation, Velocity, Acceleration, Angular Velocity, and Angular Acceleration.
Note:
If you highlight Deformation results in the tree that are scoped to rigid bodies, the corresponding rigid bodies in the Geometry window are not highlighted.
You cannot define a line body, 2D plane strain body, or 2D axisymmetric body as rigid, except that in an Explicit Dynamics analysis, 2D plane strain and 2D axisymmetric bodies may be defined as rigid.
All bodies in a body group (of a multibody part) must have the same Stiffness Behavior. When Stiffness Behavior is , the body group acts as one rigid mass regardless of whether or not the underlying bodies are topologically connected (via shared topology).