For general information about attaching a geometry to a system, see Attach Geometry/Mesh in the Mechanical User's Guide.

Solid, Surface, and Line bodies can be present in an Explicit Dynamics analysis.

Only symmetric cross sections are supported for line bodies in Explicit Dynamics analyses, except those using the LS-DYNA ACT extension. The following cross sections are not supported: T-Sections, L-Sections, Z-Sections, Hat sections, Channel Sections. For I-Sections, the two flanges must have the same thickness. For rectangular tubes, opposite sides of the rectangle must be of the same thickness.

For LS-DYNA all available cross sections in DesignModeler will be exported for analysis with the LS-DYNA solver. However, there are some limitations in the number of dimensions that the LS-DYNA solver supports for the Z, Hat and Channel cross sections. For more information, see Attaching Geometry.

To prevent the generation of unnecessarily small elements (and long run times) try using DesignModeler or SpaceClaim to remove unwanted "small" features or holes from your geometry.

Thickness can be specified for selected faces on a surface body by inserting a thickness object. Constant, tabular, and functional thickness are all supported.

Stiffness Behavior

Flexible behavior can be assigned to any body type.

Rigid behavior can be applied to Solid, Surface, and Line bodies.

Coordinate System

Local Cartesian coordinate systems can be assigned to bodies. These will be used to define the material directions when using the Orthotropic Elasticity property in a material definition. The material directions 1, 2, 3 will be aligned with the local x, y and z axes of the local coordinate system.

Reference Temperature

This option defines the initial (time=0.0) temperature of the body.

Reference Frame

Available for solid bodies when an Explicit Dynamics system is part of the solution; the user has the option of setting the Reference Frame to Lagrangian (default), Eulerian (Virtual) (not available for LS-DYNA systems), or Particle. Two additional options are available for LS-DYNA systems: S-ALE Domain and S-ALE Fill (see ALE Workflow in the LS-DYNA User's Guide for more information). Rigid Stiffness Behavior is only applicable for Lagrangian.

If the Particle reference frame is selected, the body needs to be meshed with a Particle meshing method which needs to be manually inserted and scoped to the Particle body. The body will then be solved using the SPH solver in both Explicit Dynamics and LS-DYNA systems.

Rigid Materials

For bodies defined to have rigid stiffness, only the Density property of the material associated with the body will be used. For Explicit Dynamics systems all rigid bodies must be discretized with a Full Mesh or the Rigid Body Behavior must be defined as Dimensionally Reduced. The Full Mesh option will be specified by default for the Explicit meshing physics preference.

The mass and inertia of the rigid body will be derived from the elements and material density for each body.

By default, a kinematic rigid body is defined and its motion will depend on the resultant forces and moments applied to it through interaction with other Parts of the model. Elements filled with rigid materials can interact with other regions via contact.

Constraints can only be applied to an entire rigid body. For example, a fixed displacement cannot be applied to one edge of a rigid body, it must be applied to the whole body.