Rigid Elements

  Rigid elements are modelled in FEMGEN in the same way as the other 'standard' elements. It is thus possible to generate elements such as R2D2, R3D3 or R3D4 by selecting the relevant element variant via the MESHING TYPES command.

Rigid elements must be associated with a rigid body reference node (FEMGEN point element variant 8). This is achieved by placing all geometric entities associated with the rigid body into a set whose name begins with the characters 'RBODY'. The remaining three characters of the set name can be any printable character.

The user must ensure that the normals for all elements in a rigid body definition point in the direction in which contact is anticipated. This restriction is imposed because the interface is only able to define the S1 face of plate/shell type elements as a contact surface (see section 2.12 ).

The commands 'LABEL GEOMETRY NORMAL' and VIEW HIDDEN FILL NORMAL' are useful to check this, and the 'GEOMETRY FLIP' command can be used to change the direction in which a surface faces.

  

Figure 2.7: Example Rigid Body Definition