$-----------------------------------------------------------------------
$ 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 calculates residual kinetic energy as a measure of DOF to
$ be added to the A-set. This calculation requires two runs. The first
$ is a set of FEM modes without any reduction. The second is based on
$ a preliminary A-set selection that is a subset of the final selection.
$ The residual kinetic energy provides a "measure" of which DOF should
$ be added to A-set in order to improve the ability to measure specific
$ modes. It is calculated as follows:
$
$ [DPHI] = [PHIO] - [GOT]*[PHIA] - Error in expanded mode shapes
$
$ [RKE] = [MOO]*[DPHI].^2 - Residual Kinetic energy
$
$ where
$
$ [PHIA] - A-set partition of FEM mode shapes
$ [PHIO] - O-set partition of FEM mode shapes
$ [GOT] - Guyan shapes for preliminary A-set reduction
$
$ Two runs are required. The first should use alter write_modes to write
$ the mode shapes of the full FEM. The second reads those mode shapes in
$ in various formats calculate residual kinetic energy. The
$ results are written to the .pch file in DMIG format. Each column of the
$ residual kinetic energy matrix is normalized to a maximum value of 1.0
$ in order to make it easier to identify critical DOF.
$
$ Special instructions to use this alter:
$-----------------------------------------------------------------------
$ FILE MANAGEMENT SECTION (FMS)
$
$
$ If the OUTPUT2 or OUTPUT4 options are chosen these should be assigned
$
$ 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
$
$-----------------------------------------------------------------------
$ EXECUTIVE CONTROL DECK
$
$ SOL 103
$ Include this alter immediately before the CEND statement
$
$-----------------------------------------------------------------------
$ CASE CONTROL DECK
$
$ No special input is required. The Case Control deck must include
$ standard modal solution requests (SPC, METHOD, etc.). Some output
$ request such as DISP(PLOT)=ALL is required to force data recovery.
$
$-----------------------------------------------------------------------
$ 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,KENORM,CHAR8 No: Do not normalize RKE shapes to sum of 100.0
$ Yes: Do normalize RKE shapes to sum of 100.0 (default)
$
$ PARAM,KEFILT,RS : Do not print terms less than KEFILT (default = 0.0)
$
$ PARAM,ORTHO,CHAR8 No: Do not calculate cross and pseudo orthogonality
$ Yes: Calculate and print cross and pseudo orthogonality (default)
$
$-----------------------------------------------------------------------
$ EXAMPLE NASTRAN DECKS
$
$
$ ASSIGN INPUTT4='gpsc_modes.op4' UNIT=11 OLD
$ ASSIGN MASTER='gpsc_aset.MASTER'
$ ASSIGN DBALL ='gpsc_aset.DBALL'
$ RESTART
$ $
$ SOL 103
$ INCLUDE residual_kinetic_energy.v2001
$ CEND
$ $
$ TITLE = GENERAL PURPOSE SPACECRAFT
$ SUBTITLE = NORMAL MODES DATA RECOVERY RESTART
$ LABEL = RESIDUAL KINETIC ENERGY CALCULATIONS
$ $
$ SPC = 1
$ METHOD = 50 $ Modes to 50 Hz
$ $
$ DISP(PLOT) = ALL $ Recover but don't print displacements
$ $
$ BEGIN BULK
$ $
$ PARAM,OMODES,11 $ Calculate residual kinetic energy
$ PARAM,KENORM,0 $ Normalize RKE to maximum of 1.0
$ PARAM,KEFILT,0.01 $ Do not print terms smaller than 0.01
$ $
$ ENDDATA
$
$-----------------------------------------------------------------------