/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
JXX JYY JZZ        
JXY JYZ JXZ        
Ioptoff   Ifail            
If Ifail = 1, insert the next line.
(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
= 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 Secondary nodes group identifier.

(Integer)

 
Ikrem Rigid wall deactivation flag.
= 0 (Default)
Remove rigid body secondary nodes from rigid wall.
= 1
Do not remove rigid body secondary 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 main node coordinates; the center of gravity is computed using the main and secondary node coordinates, the main node is moved to the computed center of gravity.
= 2
The center of gravity is only computed by taking into account the secondary node mass; the main 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 main node coordinates; added mass and inertia are placed on the main node coordinates; secondary node mass and inertia are transmitted to the center of gravity. The main node is not moved.
= 4
The center of gravity is set at the main node coordinates; added mass and inertia are put on center of gravity. The secondary node mass and inertia are ignored. The main node is not moved.

(Integer)

 
surf_ID Surface identifier defining the envelope surface of the rigid body.

(Integer)

 
JXX Inertia JXX.

(Real)

[ kg m 2 ]
JYY Inertia JYY.

(Real)

[ kg m 2 ]
JZZ Inertia JZZ.

(Real)

[ kg m 2 ]
JXY Inertia JXY.

(Real)

[ kg m 2 ]
JYZ Inertia JYZ.

(Real)

[ kg m 2 ]
JXZ Inertia JXZ.

(Real)

[ kg 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)

 
Ifail Failure criteria.
= 0
No failure
= 1
Failure
(Integer)
 
FN Normal force at failure.

Default = 1020 (Real)

[ N ]
FT Tangential force at failure.

Default = 1020 (Real)

[ N ]
expN Failure exponent parameter in normal direction.

Default = 2 (Integer)

 
expT Failure exponent parameter in tangential direction.

Default = 2 (Integer)

 

Comments

  1. A rigid body is set ON by default. All the elements belonging to the rigid body are deactivated in Radioss Starter.
  2. 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).
  3. 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.
  4. By default the domain decomposition will not take into account the CPU cost of these deactivated elements.
  5. 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).
  6. If sens_ID0:
    • 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.
  7. 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.
  8. 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.

  9. The envelope surface must only contain hyperellipsoids (Surfaces).
  10. Inertia is given in the skew system reference frame.
  11. By default, the global reference frame is used.
  12. /RBODY is not compatible with the rigid material (/MAT/LAW13).
  13. With Ifail=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.(1)
    ( | F N | F N ) N + ( | F S | F T ) M 1 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaubiaeqale qabaGaamOtaaqdbaWaaeWaaeaadaWcaaqaamaaemaabaWaaubeaeqa oeaacaWGobaabeqdbaGaamOraaaaaiaawEa7caGLiWoaaeaacaWGgb GaamOtaaaaaiaawIcacaGLPaaaaaGccqGHRaWkdaqfGaqabSqabeaa caWGnbaaneaadaqadaqaamaalaaabaWaaqWaaeaadaqfqaqab4qaai aadofaaeqaneaacaWGgbaaaaGaay5bSlaawIa7aaqaaiaadAeacaWG ubaaaaGaayjkaiaawMcaaaaakiabgwMiZkaaigdaaaa@4C49@
    Where,
    F N MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaqdbaWaaubeaeqaoe aacaWGobaabeqdbaGaamOraaaaaaa@37E0@
    Force in the normal direction.
    F s MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaqdbaWaaubeaeqaoe aacaWGobaabeqdbaGaamOraaaaaaa@37E0@
    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.