Block Format Keyword
/RBE3 - Interpolation Constraint Element
Description
Defines the motion of a reference (slave) node as the weighted average of the motions of sets of master nodes.
Format
(1)
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(2)
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(3)
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(4)
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(5)
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(6)
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(7)
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(8)
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(9)
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(10)
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/RBE3/rbe3_ID
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rbe3_title
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Node_IDr
|
Trarotref
|
N_set
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I_modif
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|
|
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|
|
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For each set with different weighing factors
(1)
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(2)
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(3)
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(4)
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(5)
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(6)
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(7)
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(8)
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(9)
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(10)
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WTi
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Trarot_Mi
|
skew_IDi
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grnd_IDi
|
|
|
|
|
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Field
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Contents
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rbe3_ID
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Interpolation constraint element identifier
(Integer, maximum 10 digits)
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rbe3_title
|
Interpolation constraint element title
(Character, maximum 100 characters)
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Node_IDr
|
Reference (slave) node identifier
(Integer)
|
Trarotref
|
Code of DOF used for reference node
(6 Booleans)
=0: free DOF
=1: fixed DOF
Default (blank or 6 zeros), set on all DOF
|
N_set
|
Number of different weighing factor and/or Trarot sets
(Integer)
|
I_modif
|
Modification of weighing factor flag (Comment 4)
(Integer)
Default (blank or zero), set to 1
= 1: modification is automatic
= 2: forbidden modification
= 3: change all weighing factor to unity (1.0)
|
WTi
|
Weighing factor of set i
(Real)
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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)
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grnd_IDi
|
Node group defining master nodes of set i
(Integer)
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|
(1)-1
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(1)-2
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(1)-3
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(1)-4
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(1)-5
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(1)-6
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(1)-7
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(1)-8
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(1)-9
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(1)-10
|
|
|
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TX
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TY
|
TZ
|
|
 X
|
Y
|
Z
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Field
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Contents
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TX
|
Code for translation TX
=0: free DOF
=1: fixed DOF
(Boolean)
|
TY
|
Code for translation TY
=0: free DOF
=1: fixed DOF
(Boolean)
|
TZ
|
Code for translation TZ
=0: free DOF
=1: fixed DOF
(Boolean)
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X
|
Code for rotation X
=0: free DOF
=1: fixed DOF
(Boolean)
|
Y
|
Code for rotation Y
=0: free DOF
=1: fixed DOF
(Boolean)
|
Z
|
Code for rotation Z
=0: free DOF
=1: fixed DOF
(Boolean)
|
|
| 1. | 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 weighed average. It is similar to but more general than the kinematic condition interface type 2 (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. |
| 2. | 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. |
| 3. | The absolute values of the weighing factors are not important; it is the relative values from different sets that are important since these will be normalized. |
| 4. | 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 weighing factors slightly (I_modif = 1). You can prevent this modification by setting I_modif =2.
I_modif =3 will give an equivalent behavior as /INTER/TYPE2 with Spotflag =1
| 5. | 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. |
| 6. | Hierarchy rule involving /INTER/TYPE2, /RBE2, /RBE3, and /RBODY is the following: |
RBODY > RBE3 > RBE2 > INTERFACE TYPE2
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See Also:
Implicit Features and Compatibility Information
Skew and Frame (/SKEW & /FRAME)
