Bulk Data Entry Defines a rigid body as a combination of Rigid Bodies (RBODY).


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RBADD ID REFG              
  RBODY BID1 BID2 etc. etc. etc. etc. BID7  
  MASS M              
  COG X Y Z          


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RBODY 3 1245              
  RBODY 12 13            


Field Contents SI Unit Example
BID Unique body identification number. RBADD and RBODY Bulk Data Entries cannot have the same BID.

No default (Integer > 0)

REFG Reference Grid. 6.

Default = <COG> (Integer > 0).

RBODY Flag indicating that the following list of IDs refer to Rigid Bodies defined using RBODY or RBADD.

No default

BID# Identification numbers of RBODY or RBADD entities for the preceding RBODY flag.

No default (Integer > 0)

MASS Flag to overwrite the finite element mass of the body. Indicates that a mass value is to follow.  
M Mass.

(Real > 0.0)

INERTIA Flag to overwrite the finite element inertia of the body. Indicates that the inertia properties are to follow.  
IXX,IYY,IZZ, IXY,IXZ,IYZ Moments of inertia.

For IXX, IYY, IZZ Real > 0.0

For IXY, IXZ, IYZ Real

CID Coordinate system identification number to define the orientation of the inertia tensor.
0 or blank
References the basic coordinate system.

(Integer ≥ 0 or blank)

COG Flag to overwrite the finite element center of gravity of the body. Indicates that the center of gravity information is to follow.  
X, Y, Z Location of the center of gravity.




  1. A minimum of one Rigid Body (RBODY) or RBADD should be referenced on any RBADD entry.
  2. An RBADD entry cannot reference itself recursively (with the same BID).
  3. The mass and inertia properties are defined by the finite element and mass properties specified in the corresponding RBODY's, unless they are overwritten by the mass (MASS) and inertia (INERTIA) properties specified on the continuation lines on the RBADD entry.
  4. The mass, inertia and center of gravity input are optional, if element/grid/surface information are provided in the RBODY definitions.
  5. If just the principal inertia is specified, IXX, IYY, and IZZ must be positive non-zero values and they must satisfy the sum of two inertia values must be greater than the third (IXX + IYY > IZZ, IYY+IZZ > IXX, IZZ+IXX > IYY).
  6. If MASS continuation line is specified, then either REFG or COG should be present. If MASS continuation line is not input, and both REFG and COG are not specified, the respective center of gravity of the element/grid/surface selections is used.
  7. Multiple RBADD entries with the same, as well as different identification numbers, are supported.
  8. This entry is represented as a Rigid Body in HyperMesh.