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Alter to Perform Test-Analysis Correlation


Alter Name     postmaca.alt


Purpose

To compute the cross-orthogonality between test modes and modes of
an MSC/NASTRAN model.

Two cross-orthogonality checks are made:  modal assurance criterion
(MAC) and mass orthogonality (ORTHOA).


Solution Sequence

SOL 100 (user DMAP).


Input
 
Executive Control

SOL 100
COMPILE USERDMAP
ALTER 2
INCLUDE 'postmaca.alt'
 
Case Control

No special Case Control is required.
 
Bulk Data

Several inputs are required:

1.  
DMIG entries for the analytical mode shapes (PHIEXT)
and mass matrix (MAAEXT) (output from premac).

2.  
DMIG entries (PHITEST) representing the test modal
displacements.

3.  
GRID entries for the grid points corresponding to the test
locations.


Output

There are several outputs:

        1.  
MAC.  This is in the form of a line of output for each set of
modes that are compared.

ANALYTICAL MODE 1 COMPARED TO TEST MODE 1  - MAC = 1.00
ANALYTICAL MODE 1 COMPARED TO TEST MODE 2  - MAC = 0.10
ANALYTICAL MODE 1 COMPARED TO TEST MODE 3  - MAC = 0.00

There are i times j lines of output where i is the number of
analytical modes and j is the number of test modes.

        2.  
Matrix CHECKIT.

        3.  
Matrix ORTHOA.


Limitations

None.


Sample Files

premac1.dat   10-bar cantilever beam full model that includes an
alter (pchdispa.v68), which punches the g-set modal
displacements onto file premac1.pch.

premac2.dat   10-bar cantilever beam model with an a-set for axial
and longitudinal translation of grid points 3, 5, 7, 9,
and 11.  This run includes the punched g-set
displacements (premac1.pch) from above.  MAC,
CHECKIT, and ORTHOA are computed.  "a-set"
modal displacements (PHIEXT) and mass (MAAEXT)
are punched onto file premac2.pch.

postmact.tst    Test data (PHITEST) in DMIG format that
corresponds to test mode shapes at locations
corresponding to grid points 3, 5, 7, 9, and 11 for axial
and longitudinal translations.

postmac1.dat    SOL 100 run that reads premac2.pch (analytical
results) and postmac1.tst (test data), and computes
MAC, CHECKIT, and ORTHOA.


Additional Documentation

K. Blakely and T. Rose, "Cross-Orthogonality Calculations for Pre-Test
Planning and Model Verification," 1993 MSC World Users'
Conference Proceedings, May 1993.