7.11.       MODAL_TAM Alter

 

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$  Rigid Format 103 - Normal modes analysis

$  MSC/NASTRAN Version 2001 or NX Nastran Version 1.0

$

$

$     ******************************************************

$     *****            COPYRIGHT  (C)  2003            *****

$     *****          BY ATA ENGINEERING INC.           *****

$     *****             ALL RIGHTS RESERVED            *****

$     ******************************************************

$

$     09-03- ATA/Paul Blelloch

$

$  Description:

$

$  This alter performs a Modal TAM reduction

$

$  Kammer, D.C., "Test-Analysis Model Development Using an Exact

$  Modal Reduction," The International Journal of Analytical and

$  Experimental Modal Analysis, October 1987, pp. 174-179

$

$  A Modal TAM reduction is an alternative to the static reduction

$  implemented using ASET cards in Nastran.  It uses the FEM mode shapes

$  to construct reduced mass and stiffness matrices that will predict

$  the FEM shapes as long as the shapes are linearly independent at the

$  measured (ASET) DOF.

$

$  The equations for the Modal TAM shapes are as follows:

$

$                        T        -1       T

$  GOAT  = [PHIO]*([PHIA] *[PHIA})  *[PHIA]

$

$  where:

$

$  PHIA  - A-set partition of FEM mode shapes

$  PHIO  - O-set partition of FEM mode shapes

$

$  No special processing is required to use this alter.  Simply include the

$  alter with standard ASET cards defining the reduced DOF.  If the reduced

$  mass matrix is desired it can be requested with a PARAM,EXTOUT,DMIGPCH.

$

$

$  Special instructions to use this alter:

$-----------------------------------------------------------------------

$  FILE MANAGEMENT SECTION (FMS)

$

$    The FEM mode shapes must be made available.  If these are stored in

$    OUTPUT2 or OUTPUT4 forma using the write_modes alter they must be

$    assigned using INPUTT2 or INPUTT4 cards as follows:

$

$    ASSIGN INPUTT4=fem_modes.op4 UNIT=11

$

$    or

$

$    ASSIGN INPUTT2=fem_modes.op2 UNIT=11

$

$    Note that a formatted OUTPUT4 file can be used as follows

$

$    ASSIGN INPUTT4=fem_modes.op4 UNIT=11 FORMATTED

$

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$  EXECUTIVE CONTROL DECK

$

$    SOL 103

$    Include this alter immediately before the CEND statement.

$

$-----------------------------------------------------------------------

$  CASE CONTROL DECK

$

$    No special input is required.

$

$-----------------------------------------------------------------------

$  BULK DATA DECK

$

$    Optional parameters:

$

$    PARAM,OMODES,I  <0 : Read FEM modes from OUTPUT2 file UNIT = |OMODES|

$                     0 : Read FEM modes from DMIG cards in bulk data

$                    >0 : Read FEM modes from OUTPUT4 file UNIT = OMODES

$

$    PARAM,N1,I         : 1st FEM mode to use for hybrid TAM (default = 1)

$

$    PARAM,N2,I         : Last FEM mode to use for hybrid TAM (default = all)

$

$    If the FEM modes are defined on DMIG cards, these must be included

$    in the bulk data

$

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$  EXAMPLE NASTRAN DECK

$

$

$    ASSIGN  INPUTT4='gpsc_modes.op4', UNIT=13

$    ASSIGN  MASTER='gpsc_aset.MASTER'

$    ASSIGN  DBALL ='gpsc_aset.DBALL'

$    $

$    SOL     103

$    INCLUDE modal_tam.v2001

$    CEND

$    $

$    TITLE    = GENERAL PURPOSE SPACECRAFT

$    SUBTITLE = MODAL TAM REDUCED MODES

$    LABEL    = MY ASET DOF

$    $

$    SPC = 1

$    METHOD = 50                 $ Modes to 50 Hz

$    $

$    DISP(PLOT) = ALL            $ Recover but don't print displacements

$    $

$    BEGIN BULK

$    $

$    PARAM,OMODES,13

$    $

$    ... Standard Bulk data including ASET cards ...

$    $

$    ENDDATA

$

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