/RBODY
Block Format Keyword Defines rigid bodies.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (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  I_{fail} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

FN  FT  expN  expT 
Definition
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  Main (primary) node
identifier (center of mass). (Integer) 

sens_ID  Sensor property
identifier. 6
(Integer) 

Skew_ID  Skew
identifier. (Integer) 

Ispher  Inertia flag. 8
(Integer) 

Mass  Mass. (Real) 
$\left[\text{kg}\right]$ 
grnd_ID  Secondary nodes group
identifier. (Integer) 

Ikrem  Rigid wall deactivation flag.
(Integer) 

ICoG  Center of gravity
computation flag. 7
8
(Integer) 

surf_ID  Surface
identifier defining the envelope surface of the rigid
body. (Integer) 

J_{XX}  Inertia
J_{XX}. (Real) 
$\left[\text{kg}\cdot {\text{m}}^{\text{2}}\right]$ 
J_{YY}  Inertia
J_{YY}. (Real) 
$\left[\text{kg}\cdot {\text{m}}^{\text{2}}\right]$ 
J_{ZZ}  Inertia
J_{ZZ}. (Real) 
$\left[\text{kg}\cdot {\text{m}}^{\text{2}}\right]$ 
J_{XY}  Inertia
J_{XY}. (Real) 
$\left[\text{kg}\cdot {\text{m}}^{\text{2}}\right]$ 
J_{YZ}  Inertia
J_{YZ}. (Real) 
$\left[\text{kg}\cdot {\text{m}}^{\text{2}}\right]$ 
J_{XZ}  Inertia
J_{XZ}. (Real) 
$\left[\text{kg}\cdot {\text{m}}^{\text{2}}\right]$ 
Ioptoff  Manage domain
decomposition of rigid body for Radioss
HMPP flag. 5
(Integer) 

I_{fail}  Failure criteria.


FN  Normal force at
failure. Default = 10^{20} (Real) 
$\left[\text{N}\right]$ 
FT  Tangential force at
failure. Default = 10^{20} (Real) 
$\left[\text{N}\right]$ 
expN  Failure exponent parameter
in normal direction. Default = 2 (Integer) 

expT  Failure exponent parameter
in tangential direction. Default = 2 (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 secondary 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 (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).
 With I_{fail}=1, the rigid body is deactivated when the one of failure
criteria is reached.
If the following failure criteria is reached for one secondary node.
$${{\displaystyle \left(\frac{\left{{\displaystyle F}}_{N}\right}{FN}\right)}}^{N}+{{\displaystyle \left(\frac{\left{{\displaystyle F}}_{S}\right}{FT}\right)}}^{M}\ge 1$$Where, ${{\displaystyle F}}_{N}$
 Force in the normal direction.
 ${{\displaystyle F}}_{s}$
 Force in the tangential (shear) plane.
Also, Normal direction for each secondary node is defined from the main node to the secondary node.
 Tangential direction is perpendicular to the normal direction.