/MERGE/RBODY

Block Format Keyword Defines the merging of entities to a main rigid body.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/MERGE/RBODY/merge_ID
merge_title
main_ID m_type second_ID s_type Iflag          

Definitions

Field Contents SI Unit Example
merge_ID Rigid body merge identifier.

(Integer, maximum 10 digits)

  
merge_title Rigid body merge title.

(Character, maximum 100 characters)

  
main_ID Main rigid body identifier.

(Integer, maximum 10 digits)

  
m_type Main rigid body type flag.
=0
Set to 1.
=1 (Default)
Main is an /RBODY.

(Integer)

  
second_ID Secondary rigid body identifier.

(Integer, maximum 10 digits)

  
s_type Secondary entity type flag.
= 0
Set to 1.
= 1 (Default)
Secondary is an /RBODY.
= 2
Secondary is a node ID.
= 3
Secondary is a node group (/GRNOD) identifier.

(Integer)

  
Iflag Merge option flag. 2
= 0
Set to 2.
= 1
Mass and inertia of the secondary entity is ignored. The merged rigid body will use the properties defined in the main rigid body.
= 2 (Default)
Mass and inertia of the secondary entity is added to the main rigid body. The main node position is moved to the merged rigid body new center of gravity.
= 3
Mass and inertia of the secondary entity are added to the main rigid body. The main node position is not moved, due to merging.

(Integer)

  

Comments

  1. Line 1 can be repeated to define multiple rigid body merges within one block.
  2. All secondary rigid body nodes (secondary and main) become secondary nodes of the main rigid body.
  3. Before merging, the inertia, mass, and center of gravity of each secondary and main rigid body is calculated based on their /RBODY properties. Next, the secondary entities are merged to the main rigid body and new rigid body properties are calculated based on the Iflag option.
  4. For s_type =2 (node_ID) and =3, (/GRNOD), the secondary entities can only be defined in one /MERGE/RBODY and not in any /RBODY.
  5. The main rigid body defined in a /MERGE/RBODY can be defined as a secondary rigid body in another /MERGE/RBODY. However, complex hierarchies should be avoided, as they can become difficult to debug.
  6. All kinematic conditions, initial velocity, and gravity loading applied to the secondary rigid body main node are ignored.
  7. The secondary rigid body sens_ID, Skew_ID, Ispher, Ikrem, surf_ID, and Ioptoff options are ignored. The merged rigid body will use the flags defined in the main rigid body.
  8. The merged rigid body can be activated or deactivated with /SENSOR or using the /RBODY/ON or /RBODY/OFF Engine option.
  9. If a secondary rigid body is defined in a time history output (/TH/RBODY), the main rigid body will automatically be included in the time history output, instead of the secondary rigid body.
  10. /MERGE/RBODY cannot be used with a rigid body that is the main surface of an /INTER/TYPE21 contact.