/RBE3
Block Format Keyword Defines the motion of a reference (slave) node as the weighted average of the motions of sets of master nodes.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/RBE3/rbe3_ID | |||||||||
rbe3_title | |||||||||
Node_IDr | Trarotref | N_set | I_modif |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
WTi | Trarot_Mi | skew_IDi | grnd_IDi |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
rbe3_ID | Interpolation constraint
element identifier. (Integer, maximum 10 digits) |
|
rbe3_title | Interpolation constraint
element title. (Character, maximum 100 characters) |
|
Node_IDr | Reference (slave) node
identifier. (Integer) |
|
Trarotref | Code of DOF used for
reference node.
(6 Booleans) Default (blank or 6 zeros), set on all DOF |
|
N_set | Number of different
weighting factor and/or Trarot
sets. (Integer) |
|
I_modif | Modification of weighting
factor flag. 4
Default (blank or zero), set to 1 (Integer) |
|
WTi | Weighing factor of set
i. (Real) |
|
Trarot_Mi | Master nodes' code of DOF
used in interpolation of set i. (6 Booleans) Default (blank or 6 zeros), set on all DOF |
|
skew_IDi | Local skew identifier of
set i. (Integer) |
|
grnd_IDi | Node group defining master
nodes of set i. (Integer) |
Codes for Translation and Rotation: Trarotref and Trarot_Mi
(1)-1 | (1)-2 | (1)-3 | (1)-4 | (1)-5 | (1)-6 | (1)-7 | (1)-8 | (1)-9 | (1)-10 |
---|---|---|---|---|---|---|---|---|---|
TX | TY | TZ |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
TX | Code for translation
TX.
(Boolean) |
|
TY | Code for translation
TY.
(Boolean) |
|
TZ | Code for translation
TZ.
(Boolean) |
|
Code for rotation
.
(Boolean) |
||
Code for rotation
.
(Boolean) |
||
Code for rotation
.
(Boolean) |
Comments
- This is equivalent to OptiStruct's RBE3, in which motion of a slave node depends on the motion of a group of master nodes with weighted average. It is similar to but more general than the kinematic condition interface TYPE2 (which is limited by one slave node to one master segment (3 nodes or 4 nodes) and for all translations and/or all rotation components), the slave rotation is computed as a function of translation and rotation of master nodes, if all DOF are set on in Trarot_Mi.
- It is recommended that for most applications only the translation components be used for Trarot_Mi (Spotflag =1 in /INTER/TYPE2). An exception is the case where the master nodes are co-linear and some of the slave rotation components can not be determined. In this case, some rotational component should also be set on.
- The absolute values of the weighting factors are not important; it is the relative values from different sets that are important since these will be normalized.
- All DOF of the slave node should be
determinable.
If only translation components are used for Trarot_Mi and the master nodes are quasi-collinear, numerical instability might occur in explicit analysis to avoid this; Radioss by default, will modify the input weighting factors slightly (I_modif = 1). To prevent this modification, set I_modif =2.
I_modif =3 will give an equivalent behavior as /INTER/TYPE2 with Spotflag =1.
- It is not recommended to define a hierarchy involving RBE3, with other constraint equation (kinematic conditions; however, this is permitted, if the hierarchy rule has been respected.
- Hierarchy rule involving
/INTER/TYPE2, /RBE2,
/RBE3, and /RBODY
is:
RBODY > RBE3 > RBE2 > INTERFACE TYPE2