External Super Element Nastran

MSC.Software VPD Conference | July 17-19, 2006 | Huntington Beach, California

External Superelements in MSC Nastran, a Super Tool for Segmented Optics

Victor Genberg, Gary Bisson, Gregory Michels, Keith DoyleSigmadyne, Inc.

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Introduction

• Problem: Creating system level models from component models• Component models may be from multiple sources/vendors• Conflicting numbering schemes (Grids, Elements, Properties, etc)• Conflicting coordinate systems (inconsistent use of Basic)• Creating multiple instances of a component from a single model

• (copying, renumbering everything, requires model checking)

• Maintaining documentation and heritage of component models• (references to grid & element numbers, comments in bulk data)

• Model checkout and verification required after any changes

• Solution: MSC Nastran External Superelements• “Super” tool for model assembly

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Example Application: NASA James Webb Space Telescope (JWST)

Primary Mirror18 segments Science

Instruments

Secondary Mirror

Deployed Stowed

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Primary Mirror Segment Assembly - treated as SuperElement

3 point attachmentto residual structure

Viewed from back side

1 of 18 Petals

130,000 grids

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Supports 18 mirror segmentsand all other components

Back Plane = Residual Structure

StowedConfiguration

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• Telescope assembly model:• Primary mirror (18 segments)

• only 1 detailed segment model available; needed 18• 130,000 grids and elements in 1 segment

• numbering scheme conflicted with other component models• not intended for assembly into an assembly model

• use of Basic coordinate system conflicted with other components• Grid CD,CP left blank

• Other components to be integrated• Back Plane structure to support Primary Mirror• Secondary Mirror assembly• Aft Optical Structure• Science Instruments

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Superelements in Statics/Dynamics in MSC Nastran

1) Conventional SE: all data in ‘main bulk data’- Typically build all models into 1 database with no numbering conflicts. - Must keep track of database versions, lots of bookkeeping

2) Manual K & M matrices:- Reduce component to Kaa, Maa, Pa - punch matrix, or send to OP2- Simple, clean, no database required; no internal SE output

3) Part SE:- Merge models with conflicting Ids - use ‘BEGIN SUPER”- Automatic joining, great for contractor models

4) External SE: (all advantages of Part SE)- Process single SE per run - save database- Can pass any extra internal SE output to residual run by OTM- OTM = Output Transformation Matrix

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MSC Nastran External Superelements

• Advantages• Allows conflicting numbering schemes in components• Allows easy creation of multiple instancing

• A single reduced SE can be copied in 18 times• Exception: for static loading orientation & magnitude reduce 18 times

• Very simple database management • No need to keep detailed records like conventional SE• Smaller individual databases, not one large master database

• Minimal changes to a vendor supplied component model • Maintain heritage of component model • Maintain Numbering, Comments in bulk data

• Automated output using EXTSEOUT• Disadvantage

• Need to chose SE output at reduction run for OTM

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MSC Nastran External Superelements

• Case Control required: • EXTSEOUT• Output requests for OTM (Output Transformation Matrices)• Include loading to match residual cases

• Bulk Data required• ASET = Boundary points and any other grids passed to residual

• (3 attach points per segment)

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Creating an External Superelement

• Single CASE CONTROL command

BOLD defines the defaultsFormat:

EXTSEOUT [([STIFFNESS, MASS, DAMPING, K4DAMP, LOADS,ASMBULK, EXTBULK, EXTID = seid,])]

⎪⎪⎭

⎪⎪⎬

⎫

⎪⎪⎩

⎪⎪⎨

⎧

=DMIGPCHDMIGOPDMIGDB

unit2

MATRIXDB

Options for superelement connection

Storage method

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Creating an External Superelement (cont)

• My preferred use

EXTSEOUT(ASMBULK,EXTBULK,EXTID=10)

• Creates a DBALL with K,M,B,K4,P (if they exist)• Nastran job scr=no (save database: job.master and job.dball)

• Automatic Output Transformation Matrices (OTMs)• Based on Case Control command in Reduction run

• DISP=nn or STRESS=nn (nn=set #)

• Creates “.asm” file for assembly main bulk data (ASCII file)• Creates “.pch” file for assembly part bulk data (ASCII file)

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External SE: New Case Control - cont’d

• Definition: OTM = Output Transformation Matrix:

• The contents of OTM are based on Case Control output requests of SPCFORCE, DISPLACEMENT, STRESS and FORCE only. (NOTE NO MPCF capability). This selection must be done during reduction run to create OTM.

• Example Case Control for SE reduction run:• Set 99 = 102,155• disp=99

• Residual structure run• Subcase 10• super=10• set 99=102,155• disp=99

Create OTM inReduction run

Obtain SE outputin residual run

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Multiple Instances – from single componentB3

4 5

6

12

3

1

2

3 4

5

6

A1

B1

4

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6 1

2

3

56

1

2 3

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C6

1

23

4

5 6

A5

B5

4

56

1

2 3

5

6

12

3

4

C4

1

2

34

5

6

A4

B4

4

5

61

2

3

5 6

1

23

4

C31 2

3

45

6 A35

6 1

2

34C2

1

2 3

4

56

A2

B2

4

5 6

1

23

5

6

1 2

3

4C1

12

3

4 5

6

A6

B6

45

6

1 2

35

61

2

3 4C5 V2

V3

V1

Y

X

Y

X

Y

XY

XY

XY

X

YX

Y

X

YX

Y

X

Y

X

YX

Y

X

Y

X

YX

Y

X

Y

X

YX

6-1

4-5

3-4

2-3

1-2

1-2

1-2

1-2

1-2

1-2

1-2

1-2

1-2

1-2

1-2

1-2

1-21-2

1-2

1-21-2

1-2

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

2-3

3-4

3-4

3-4

3-4

3-4

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3-4

3-4

3-4

3-4

3-4

3-4

3-43-4

3-4

3-4

3-4

4-5

4-5

4-5

4-5

4-54-5

4-5

4-5

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4-5

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4-5

4-5

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4-5

4-5

5-6

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5-6

5-6

5-6

5-65-6

5-6

5-6

5-6

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5-6

5-6

5-6

5-6

5-6

6-1

6-1

6-1

6-1

6-1

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6-1

6-1

6-1

6-1

6-1

6-1

6-1

6-1

6-1

6-1 6-1

A single model ofa segment is reduced.Boundary Grids =9000001-3

To place reduced SEin each location, useSECONCT to joinSE 9000001-3to residual grids900jj01-3 wherejj = segment # = 01-18

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Typical SE Reduction Run - Run for each SE because of load variation

assign master='se18-redux.MASTER' deleteassign dball='se18-redux.DBALL' deletesol 101...extseout(asmbulk,extbulk,extid=18)disp=1subcase 4load=4...begin bulkaccel,4,0,9.80665,0.,0.,z,-3.290,1.12,4.112,1.68

$ all references to basic replaced with 2222cord2r 2222 9001800 0.0 0.0 0.0 0.0 0.0 1.0

1.0 0.0 0.0$ Attach points: GRID 9000001 9001802 .4582 -90. -.199063 9001802 GRID 9000002 9001802 .4582 30. -.199063 9001802 GRID 9000003 9001802 .4582 150. -.199063 9001802 $ vertexGRID 9000000 9001800 0. 0. 0. 9001800

aset1,123456,9000000,9000001,9000002,9000003

include rest of SE model

Save matrices on database, send other to

ASCII files

Locate each by Segment Coord Sys

Global substitutionof 90017 for 90018will create SE 17

reduction run

OTMOutput SurfaceDisplacements

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EXTSEOUT output: asm file (This becomes part of residual structure)

$ .ASM FILE FOR EXTERNAL SUPERELEMENT 18$ --------------------------------------------$SEBULK 18EXTERNAL MANUAL$SECONCT 18 0

9000000 9001800 9000001 9001801 9000002 9001802 9000003 9001803

$CORD2R 9001802 .150629-1.14231 1.97855 .162125-3.15884 .894249

2.41735-.979507 1.69981 $$ BOUNDARY GRID DATA$GRID 9001800 9001800 0. 0. 0. 9001800 GRID 9001801 9001802 .4582 -90. -.199063 9001802 GRID 9001802 9001802 .4582 30. -.199063 9001802 GRID 9001803 9001802 .4582 150. -.199063 9001802

Renumber toLocate Segment

Renumber forEach Segment

SE GridResidual

Grid

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EXTSEOUT output: pch file (SE numbering, may conflict)

$ .PCH FILE FOR EXTERNAL SUPERELEMENT 18$ --------------------------------------------$BEGIN SUPER 18$CORD2R 9001802 .150629-1.14231 1.97855 .162125-3.15884 .894249

2.41735-.979507 1.69981 $EXTRN 9000000 123456 9000001 123456 9000002 123456 9000003 123456$$ BOUNDARY GRID DATA$GRID 9000000 9001800 0. 0. 0. 9001800 GRID 9000001 9001802 .4582 -90. -.199063 9001802 GRID 9000002 9001802 .4582 30. -.199063 9001802 GRID 9000003 9001802 .4582 150. -.199063 9001802 $ASET 9000000 123456 9000001 123456 9000002 123456 9000003 123456

No changesrequired

These Grid# may

conflict from SE to SE

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Residual Run

assign se18='se18-redux.MASTER'dblocate db=(extdb) convert(seid=18) logi=se18sol 101disp=1subcase 4load=4

...begin bulkaccel,4,0,9.80665,0.,0.,z,-3.290,1.12,4.112,1.68

$ include connectors from SE to Residualinclude 'connectors.bdf'$$ include seconct: se-to-residual$ change 9000001-3 to 900jj01-3include ’se18-redux.asm'$$ external se aset: grids & coord & EXTRN orderinclude 'se18-redux.pch'enddata

Include all18 SE

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Post-Process Surface Displacements in SigFitsurface fitting program

Use Sigmadyne/SigFit to:

• Calculate Surface RMS

• Fit Zernike polynomials

• Adaptive Control

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Comments

• In the previous example, all 18 segments are reduced individually• Inertial loads are position dependent, thus vary between SE• Requires separated reduction for each SE, with proper CORD system• All input files easily created from the first SE file by global

substitution

• If the loads were identical in all segments, only 1 reduction req’d• Each segment uses the same reduced matrices• In the Residual run, each SE points at the same reduced SE database

• In dynamic analysis, only 1 Craig-Bampton reduction required• Each segment uses the same reduced matrices• In the Residual run, each SE points at the same reduced SE database

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Comments

• Recent MSC Nastran enhancements useful in External SE

• param,automset,yes• will automatically rearrange DOF in M-set to free up ASET DOF• example: RBE3 dependent DOF can be on ASET (no need for “um”)

• param,autoqset,yes• will automatically create the proper number of SPOINTS and SEQSET for

Component Mode Synthesis

• resvec (case control)• turn on residual flexibility in SE and/or Residual

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Modeling Recommendations

1) Assume models will be incorporated into system level SE models- Plan ahead: break-up, numbering scheme, coord-sys

2) Create self-contained component bulk data files - Compact & consistent numbering scheme- Reference everything back to single Local coordinate system

for easy re-positioning (do NOT use basic=0)- Each component should be able to run as stand-alone

3) Join components with coincident grids and RBARs or CBUSH- Place RBAR/CBUSH connectors in a separate file- CBUSH allows model tuning and I/F force output

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Conclusions

• External SE: a “SUPER” tool for telescopes with segmented optics• Allows for easy assembly of models with incompatible numbering• Allows swapping of component models for easy updating / variations

• Components updated and swapped without affecting remainder

• Smaller databases with less bookkeeping than conventional SE• Automated generation of “asm” and “pch” files using EXTSEOUT• Allows multiple instancing of repeating components

• especially convenient for a segmented mirrors

• Superelement reduction is efficient in optical structures• Components are kinematically mounted for isolation• Reduced matrices are small because of 3-point mounts

Documents

External Super Element Nastran