/RBODY

Block Format Keyword Defines rigid bodies.

Format

(1)	(2)	(3)	(4)	(5)	(7)	(8)	(9)	(10)
/RBODY/`rbody_ID`/`unit_ID`
`rbody_title`
`node_ID`	`sens_ID`	`Skew_ID`	`Ispher`	`Mass`	`grnd_ID`	`Ikrem`	`ICoG`	`surf_ID`
`J`_XX		`J`_YY		`J`_ZZ
`J`_XY		`J`_YZ		`J`_XZ
`Ioptoff`

Definitions

Field	Contents	SI Unit Example
`rbody_ID`	Rigid body identifier (Integer, maximum 10 digits)
`unit_ID`	Unit Identifier (Integer, maximum 10 digits)
`rbody_title`	Rigid body title. (Character, maximum 100 characters)
`node_ID`	Master (primary) node identifier (center of mass). (Integer)
`sens_ID`	Sensor property identifier. 6 = 0 No sensor is used (Integer)
`Skew_ID`	Skew identifier. (Integer)
`Ispher`	Inertia flag. 8 = 0 Set to 2. = 1 Inertia is set spherical. = 2 (Default) Inertia is computed and will be automatically corrected, if the inertia is not physical. = 3 Inertia is computed as input with no automatic changes. (Integer)
`Mass`	Mass. (Real)	$[kg]$
`grnd_ID`	Slave nodes group identifier. (Integer)
`Ikrem`	Rigid wall deactivation flag. = 0 (Default) Remove rigid body slave nodes from rigid wall. = 1 Do not remove rigid body slave nodes from rigid wall. (Integer)
`ICoG`	Center of gravity computation flag. 7 8 = 0 Set to 1. = 1 (Default) Mass and inertia are added at the master node coordinates; the center of gravity is computed using the master and slave node coordinates, the master node is moved to the computed center of gravity. = 2 The center of gravity is only computed by taking into account the slave node mass; the master node is moved to the computed center of gravity, added mass and inertia are placed at the center of gravity. = 3 The center of gravity is set at the master node coordinates; added mass and inertia are placed on the master node coordinates; slave node mass and inertia are transmitted to the center of gravity. The master node is not moved. = 4 The center of gravity is set at the master node coordinates; added mass and inertia are put on center of gravity. The slave node mass and inertia are ignored. The master node is not moved. (Integer)
`surf_ID`	Surface identifier defining the envelope surface of the rigid body. (Integer)
`J`_XX	Inertia `J`_XX (Real)	$[kg \cdot m^{2}]$
`J`_YY	Inertia `J`_YY (Real)	$[kg \cdot m^{2}]$
`J`_ZZ	Inertia `J`_ZZ (Real)	$[kg \cdot m^{2}]$
`J`_XY	Inertia `J`_XY (Real)	$[kg \cdot m^{2}]$
`J`_YZ	Inertia `J`_YZ (Real)	$[kg \cdot m^{2}]$
`J`_XZ	Inertia `J`_XZ (Real)	$[kg \cdot m^{2}]$
`Ioptoff`	Manage domain decomposition of rigid body for Radioss HMPP flag. 5 = 0 (Default) CPU cost of elements associated with rigid body is not taken into account for domain decomposition load-balancing. = 1 CPU cost of elements associated with rigid body is taken into account for domain decomposition load-balancing. (Integer)

Comments

A rigid body is set ON by default. All the elements belonging to the rigid body are deactivated in Radioss Starter.
If the Ipri flag defined in /IOFLAG has a value greater than or equal to 5, a list of deactivated elements is written in the Starter output file (_0000.out).
This optimization is not done if a rigid body is defined with a sensor (sens_ID ≠ 0), in which case the elements will not be deactivated.
By default the domain decomposition will not take into account the CPU cost of these deactivated elements.
If Ioptoff is set to 1, the domain decomposition will continue to take into account the CPU cost of these elements, as they will be reactivated (worth using when the rigid body is set to OFF in Engine Input).
If sens_ID≠ 0:
- The rigid body is activated and deactivated by the sens_ID;
- The added mass (Mass) and added inertia (Lines 4 and 5) are not used;
- The center of gravity computation (ICoG) flag is ignored;
- The rigid wall deactivation (Ikrem) flag is equal to 1;
- The rigid body is active (not active) when the sensor is not active (respectively, active);
- At the beginning of the simulation (time t=0), the rigid body is activated, as long as the sensor is not active;
- In order to deactivate the rigid body at the beginning of the simulation (from time t=0), use a sensor that is active at time t=0.
If a rigid body is activated using the Radioss Engine option /RBODY, the center of the gravity computation (ICoG) flag is then ignored; the rigid body is activated with respect to ICoG =2 characteristics.
Ispher, inertia flag.
If the ratio of the maximum principal inertia to the minimum principal inertia is greater than 1000, the default option Ispher = 2 will add 10% of the maximum principal inertia to the minimum principal. This improves the model stability.

The spherical inertia option Ispher = 1 is recommended when a rigid body is a similar size or smaller than the elements to which it is connected. One example is a rigid body with two slave nodes. This helps with the stability of the connected elements, if a rigid body has the same order of size or is smaller than the elements to which it is connected.
The envelope surface must only contain hyperellipsoids (see Surfaces).
Inertia is given in the skew system reference frame.
By default, the global reference frame is used.
/RBODY is not compatible with the rigid material (/MAT/LAW13).