7.12.       ORTHO Alter

 

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

$  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 pseudo and cross-orthogonality of a set of FEM

$  mode shapes and optionally a set of test mode shapes with respect to a

$  TAM reduced mass matrix and shapes.

$

$  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 order to calculate pseudo and cross-orthgonality.  If test mode shapes

$  are available that need to be included on DMIG cards.

$

$  The FEM pseudo-orthogonality is defined as follows:

$

$              T

$  PORTHO = PHI    * MAA * PHI

$              FEM            FEM

$

$  WHERE:

$

$  PHI     - FEM mode shapes partitioned to A-set DOF

$     FEM

$

$  MAA     - TAM mass matrix

$

$  By default the FEM modes are not normalized before this calculation, so the

$  diagonals are not necessarily 1.0.  This provides a measure of the accuracy

$  of the reduction.  Optionally they can be renormalized to 1.0 on the diagonals

$  by using PARAM,NORMFEM.  This provides a calculation that is consistent with

$  most implementations of cross-orthogonality.

$

$  The cross-orthogonality is defined as follows;

$

$

$              T

$  XORTHO = PHI    * MAA * PHI

$              TAM            FEM

$

$  WHERE:

$

$  PHI     - TAM mode shapes

$     TAM

$

$  If test mode shapes are available the pseudo-orthogonality of the test

$  shapes, and the cross-orthogonality between the test and FEM shapes are

$  also calculated.

$

$  See 'write_modes' alter for more on options for writing FEM mode shapes

$

$  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,MAC,CHAR8   'YES' : Calculate Pseudo and Cross MAC

$                      'NO'  : Do not calculate Pseudo and Cross MAC (Default)

$

$    PARAM,NORMFEM,CHAR8 'YES' : Normalize FEM modes to ASET mass matrix

$                        'NO'  : Do not renormalize FEM modes (Default)

$

$    PARAM,TMODORT,CHAR8 'YES' : Orthogonalize Test Modes using Barach's Method

$                        'NO'  : Do not orthogonalize test modes (Default)

$

$    PARAM,RESFOR,CHAR8  'YES' : Calculate residual forces and MRPT stiffness

$                        'NO'  : Do not calculate residual forces

$

$    PARAM,WRTOP4,CHAR8  'YES' : Write perturbation matrices in OP4 format

$                        'NO'  : Do not write perturbation matrices in OP4 format (default)

$

$    PARAM,WRTMOD,CHAR8  'YES' : Write mode shapes and mass matrix to OUTPUT4 file

$                        'NO'  : Do not write mode shapes and mass matrix OP4 format (default)

$

$    If the FEM shapes are included on DMIG cards in bulk data they must be

$    named UGFEM.  A matrix FLAMA with the frequencies in the 1st row must

$    also be included on DMI cards.

$

$    If test mode shapes are included, they must be named PHITEST on DMIG cards,

$    and a matrix TLAMA with the test frequencies in the 1st row must also

$    be included on DMI cards.

$

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

$  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 ortho.v2001

$    CEND

$    $

$    TITLE    = GENERAL PURPOSE SPACECRAFT

$    SUBTITLE = NORMAL MODES DATA RECOVERY RESTART

$    LABEL    = CALCULATE PSEUDO AND CROSS-ORTHOGONALITY

$    $

$    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

$    $

$    ENDDATA

$

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