Interpolation Constraint Element
Description: Defines the motion at a reference grid point as the weighted average of the motions at a set of other grid points.
Format:
Example:
| Field | Definition | Type | Default |
|---|---|---|---|
| EID | Element identification number. | Integer > 0 | Required |
| REFGRID | Reference grid point identification number. | Integer > 0 | Required |
| REFC | Component numbers at the reference grid point. (Up to six unique digits may be placed in the field with no embedded blanks.) | 1 ≤ Integers ≤ 6 | Required |
| WTi | Weighting factor for components of motion at grid points Gi,j. | Real | Required |
| Ci | Component numbers with weighting factor WTi at grid points Gi,j. (Up to three unique digits may be placed in the field with no embedded blanks.) | 1 ≤ Integers ≤ 6 | Required |
| Gi,j | Grid points whose components Ci have weighting factor WTi in the averaging equations. | Integer > 0 | Required |
| GMi | Grid points whose components CMi are to be made dependent. See Remark 7. | Integer > 0 | Required |
| CMi | Component numbers of GM. (Up to six unique digits may be placed in the field with no embedded blanks.) See Remark 7. | 1 ≤ Integers ≤ 6 | Required |
Remarks:
- Components Ci at grid points Gi,j must be able to react rigid body motion resulting from REFC. For most applications components 123 can be specified for Ci, except when Gi,j is collinear. In the latter case, only the inplane components should be specified.
- Blank spaces may be left at the end of a Gi,j sequence.
- By default, a dependent degree of freedom assigned by one element cannot be assigned dependent by another rigid element or MPC entry and cannot be additionally constrained (e.g., single-point constraint). If this behavior is desired use PARAM, AUTOFIXRIGIDSPC which when set to ON will allow the constraint of dependent degrees of freedom. (See Section 5, Parameters, for more information on AUTOFIXRIGIDSPC.)
- Degrees of freedom declared to be independent by one rigid body element can be made dependent by another rigid body element or by a multipoint constraint.
- Rigid elements, unlike MPCs, are not selected through the Case Control Section.
- Forces of multipoint constraint may be recovered with the MPCFORCES Case Control command.
- The purpose of the GMi and CMi fields are to replace dependent reference degrees of freedom with independent ones which can be either assigned dependent by another rigid element or MPC entry or be additionally constrained (e.g., single-point constraint). Specification of these degrees of freedom can result in the generation of invalid MPC equations and subsequent fatal errors. The preferred method is the use of PARAM, AUTOFIXRIGIDSPC which when set to ON will allow the constraint of dependent degrees of freedom. (See Section 5, Parameters, for more information on AUTOFIXRIGIDSPC.)