7.2.           DYNAMIC_TAM

 

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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 dynamic TAM reduction

$

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

$  implemented using ASET cards in Nastran.  Rather than develop the

$  reduction matrices using only stiffness terms, it adds mass terms.

$  It is based on choosing a "center" frequency, and it is exact only

$  at that frequency.

$

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

$

$                     2       -1           2

$  GOAT  = -([KOO] - W *[MOO])  *([KOA] - W [MOA])

$

$  where:

$

$  W     - Center frequency chosen by user (converted to radians/sec)

$

$  Note:  The center frequency should never be higher than the 1st mode of the

$  O-set.  To find this frequency you can fix (SPC) all the ASET DOF and do

$  a modal calculation.

$

$  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.

$  The parameter DFREQ is required to select the center frequency for the

$  reduction.

$

$

$  Special instructions to use this alter:

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

$  FILE MANAGEMENT SECTION (FMS)

$

$    No special input is required.

$

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

$  EXECUTIVE CONTROL DECK

$

$    SOL 103

$    Include this alter immediately before the CEND statement.

$

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

$  CASE CONTROL DECK

$

$    No special input is required.

$

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

$  BULK DATA DECK

$

$    Required parameter:

$

$    PARAM,DFREQ,RS : Central Frequency in Hz (no default)

$

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

$  EXAMPLE NASTRAN DECK

$

$

$    ASSIGN  MASTER='gpsc_aset.MASTER'

$    ASSIGN  DBALL ='gpsc_aset.DBALL'

$    $

$    SOL     103

$    INCLUDE dynamic_tam.v2001

$    CEND

$    $

$    TITLE    = GENERAL PURPOSE SPACECRAFT

$    SUBTITLE = DYNAMIC TAM REDUCED MODES

$    LABEL    = 20 Hz CENTER FREQUENCY

$    $

$    SPC = 1

$    METHOD = 50                 $ Modes to 50 Hz

$    $

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

$    $

$    BEGIN BULK

$    $

$    PARAM,DFREQ,20.0            $ Set center frequency to 20 Hz

$    $

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

$    $

$    ENDDATA

$

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