For general information about defining parts, see Define Part Behavior in the Mechanical User's Guide.
Nonlinear effects are always accounted for in Explicit Dynamics analysis.
Parts may be defined as rigid or flexible. In the solver, rigid parts are represented by a single point that carries the inertial properties together with a discretized exterior surface, which represents the geometry. Rigid bodies should be meshed using similar Method mesh controls as those used for flexible bodies. The inertial properties used in the solver will be derived from the discretized representation of the body and the material density. Therefore, it may differ slightly from the values presented in the properties of the body in the Mechanical application GUI.
At least one flexible body must be specified when using the Explicit Dynamics solver. The solver requires this in order to calculate the time-step increments. In the absence of a flexible body, the time-step becomes underdefined. The boundary conditions allowed for the rigid bodies with Explicit Dynamics are:
Connections
Contact Regions: Frictionless, Frictional and Bonded.
Body Interactions: Frictionless, Frictional and Bonded. Bonded body interactions are not supported for LS-DYNA.
In Explicit Dynamics systems, rigid bodies may not be bonded to other rigid bodies.
Initial Conditions: Velocity, Angular Velocity
Supports: Displacement, Fixed Support and Velocity.
Loads: Pressure and Force. Force is not supported for Explicit Dynamics analyses.
For an Explicit Dynamics analysis, the following postprocessing features are available for rigid bodies:
Results and Probes: Deformation only - that is, Displacement, Velocity.
Result Trackers: Body average data only.
If a multibody part consists only of rigid bodies, all of which share the same material assignment, the part will act as a single rigid body, even if the individual bodies are not physically connected.