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