$-----------------------------------------------------------------------
$ 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
$
$ 07-18-06 ATA/George Antoun
$ o Now writes initial user-defined ASET to punch file
$
$ Description:
$
$ This alter performs an Iterative Residual Kinetic Energy scheme to optimally
$ select A-set DOF. It starts from a small A-set defined by the user and
$ iteratively adds DOF until it reaches a user specified number. At
$ each iteration it add the DOF with the highest residual kinetic energy
$ across all FEM modes.
$
$ The number of DOF eliminated at each step of the iterative process is
$ controlled by the parameter GUFILT. The default value of 1.0 will
$ eliminate one DOF at each step. Setting GUFILT to a value less than
$ 1.0 may result in a larger number of DOF eliminated at each iterative
$ step. All DOF with a stiffness/mass ratio greater than GUFILT times
$ the largest ratio are eliminated at each step.
$
$ If the value of GUFILT results in deleting enough DOF that the
$ remaining number is less than NGUYAN at any step it is internally
$ reset to 1.0. From this point on one DOF will be eliminated at all
$ following steps.
$
$ Currently this alter will calculate the eigenvalues for the reduced
$ mass and stiffness matrices, but will then fail. It will write the
$ selected DOF list to the PCH file. This can be used to create ASET
$ cards to perform a Guyan reduction.
$
$ Special instructions to use this alter:
$-----------------------------------------------------------------------
$ FILE MANAGEMENT SECTION (FMS)
$
$ If no ASET is defined, a considerable amount of scratch space may be
$ required. This may require the addition of a card of the following
$ form
$
$ INIT SCRATCH LOGICAL=(SCR1(20GB)),
$ SCR300=(SCR300(20GB))
$
$-----------------------------------------------------------------------
$ 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,NGUYAN,I : Number of DOF in final set (no default)
$
$ PARAM,GUFILT,RS : Filter to remove DOF at each step (default = 1.0)
$
$ PARAM,OMODES,I <0 : Read FEM modes from OUTPUT2 file UNIT = |OMODES|
$ 0 : Do not calculate orthogonality (no FEM modes)
$ >0 : Read FEM modes from OUTPUT4 file UNIT = OMODES
$
$-----------------------------------------------------------------------
$ EXAMPLE NASTRAN DECKS
$
$
$ ASSIGN MASTER='gpsc_aset.MASTER'
$ ASSIGN DBALL ='gpsc_aset.DBALL'
$ $
$ SOL 103
$ INCLUDE iter_guyan.v2001
$ CEND
$ $
$ TITLE = GENERAL PURPOSE SPACECRAFT
$ SUBTITLE = SELECT DOF
$ LABEL = ITERATIVE GUYAN REDUCTION METHOD
$ $
$ SPC = 1
$ METHOD = 50 $ Modes to 50 Hz
$ $
$ BEGIN BULK
$ $
$ PARAM,NGUYAN,50 $ Select best 50 DOF
$ PARAM,GUFILT,0.9 $ Eliminate DOF with > 90% of max ratio
$ $
$ EIGR,50,AHOU,1.0,50.0
$ $
$ INLCUDE 'gpsc.blk'
$ $
$ ENDDATA
$
$-----------------------------------------------------------------------