RBE3 – Interpolation Constraint Element
Defines the motion at a "reference" grid point as the weighted average of the motions at a set of other grid points.
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(2) |
(3) |
(4) |
(5) |
(6) |
(7) |
(8) |
(9) |
(10) |
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RBE3 |
EID |
blank |
REFGRID |
REFC |
WT1 |
C1 |
G1,1 |
G1,2 |
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G1,3 |
WT2 |
C2 |
G2,1 |
G2,2 |
etc. |
WT3 |
C3 |
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G3,1 |
G3,2 |
etc. |
WT4 |
C4 |
G4,1 |
G4,2 |
etc. |
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"UM" |
GM1 |
CM1 |
GM2 |
CM2 |
GM3 |
CM3 |
blank |
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blank |
GM4 |
CM4 |
GM5 |
CM5 |
etc. |
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blank |
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(2) |
(3) |
(4) |
(5) |
(6) |
(7) |
(8) |
(9) |
(10) |
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RBE3 |
14 |
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100 |
1234 |
1.0 |
123 |
1 |
3 |
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5 |
4.7 |
1 |
2 |
4 |
6 |
5.2 |
2 |
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7 |
8 |
9 |
5.1 |
1 |
15 |
16 |
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UM |
100 |
14 |
5 |
3 |
7 |
2 |
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Field |
Contents |
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EID |
Unique element identification number. |
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REFGRID |
Reference grid point. This is the dependent GRID. Some, or all, of the dependent degrees-of-freedom of this grid can be made independent by redefining all of the dependent degrees-of-freedom following the UM flag. (Integer > 0) |
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REFC |
Global components of motion whose values will be computed at the reference grid point. Any of the digits 1, 2, ..., 6 with no embedded blanks. (Integer > 0) |
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WTi |
Weighting factor for components of motion on the following entry at grid points Gi,j. (Real) |
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Ci |
Global components of motion that have weighting factor WT, at grid points Gi,j. Any of the digits 1, 2, ..., 6, with no embedded blanks. (Integer > 0) |
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Gi,j |
Grid point whose components Ci have weighting factor WTi in the averaging equations. (Integer > 0) |
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UM |
Optional flag indicating that a data set redefining the entire dependent degree-of-freedom set is to follow. The default is that all of the components in REFC at the reference grid point form the dependent degree-of-freedom set. |
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GMi |
Grid points with components in the redefined dependent degree-of-freedom set. (Integer > 0) |
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CMi |
Components of motion at GMi in the redefined dependent degree-of-freedom set. Any of the digits 1 through 6, with no embedded blanks. (Integer > 0) |
It is recommended that for most applications only the translation components 123 be used for Ci. An exception is the case where the Gij are collinear. A rotation component may then be added to one grid point, to stabilize its associated rigid body mode for the element.
Blank spaces may be left at the end of a Gij sequence.
The default for the dependent degree-of-freedom set should be used except in cases where you want to redefine some or all REFC components as the dependent degree-of-freedom set. If the default is not used for the dependent degree-of-freedom set:
- The total number of components therein (i.e., the total number of dependent degrees of freedom defined by the element) must be equal to the number of components in REFC (four components in the example).
- The components therein must be a subset of the components mentioned in REFC and Gij_Ci.
- The coefficient matrix [Rm] in the constraints equation [RM] {um} + [Rn] {un} = 0 must be nonsingular, where um denotes the dependent degree-of-freedom set and un denotes the independent degree-of-freedom set.
Dependent degrees of freedom assigned by one rigid element may not also be assigned dependent by another rigid element or by a multi-point constraint, and may not be specified on SPC data.
In version 5.0, the RBE3 element calculation was modified in order to make the results independent of the units used in the model. For this purpose, the weights of the rotational degrees of freedom have been scaled by the square of the average distance between the independent grid points and the reference point. This change will only affect the results if independent grid points with rotational degrees of freedom exist in the RBE3 element. The previous RBE3 formulation can be enforced with the debug statement debug,OLDRBE3,1.0.
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Guidelines for Bulk Data Entries
Alphabetical List of Bulk Data Entries