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Alters to Perform Coupled Dynamic Analysis

Alter Name

alter1ga.v707
alter2ga.v707
alter3ga.v707
alter9ga.v707

Purpose

These DMAP Alters are used in creating a reduced model of a
component using the "Craig-Bampton" method of component modal
synthesis.  A special feature of these files is that they create output
transformation matrices (OTM) for displacements, forces, and
stresses.  They also allow for "assembly plots" that include a
"skeleton" for the component.  This skeleton is based on grid points
selected during the processing of the component.  The DMAP Alters
are:
 
alter1ga.v69 (SOL 103) - Creates reduced models (often
referred to as `Craig-Bampton' models) of components using
superelements.  Includes creation of transformation matrices
for output quantities. 
 
alter2ga.v69 (SOL 103) - Reads the matrices created by
alter1g into MSC/NASTRAN and stores them as a
superelement.
 
alter9ga.v69 (SOLs 111 and 112) - Calculates the boundary
forces for a superelement and calculates the results using
transformation matrices (includes sebloada.v69).


Solution Sequences

SOLs 103, 111, and 112.


Input

Call MSC and request a copy of the documentation.


Output

Standard MSC/NASTRAN output plus the results of the
transformation matrices and selected boundary forces.  The output for
the superelement displacements is in standard MSC/NASTRAN
format, and deformed plots using the selected set of grid points are
possible.


Limitations

The user must select any grid points that are used for plotting or
loading the reduced model.

Output resulting from the OTM is not labeled.  The user must use the
results of the initial run to create a table that correlates the terms in
the OTM to the physical quantities represented.


Sample Files

The following files perform the creation, importing, and analysis of a
cantliever beam model using the Craig-Bampton method to reduce
the outer half into a set of matrices. 
 
alterg1.dat - Baseline model, a full model with no
superelements.
 
alter1g1.dat - Creates reduced matrices and transformations
for tip superelement 10 (normally performed by contractor). 

alter1g1.pch - edited punch file from cbar1g. Used as input for alter2g1.dat
 
alter2g1.dat - Reads reduced matrices for superelement 10
and stores them (normally performed by system integrator).
 
alter3g1.dat - Performs assembly eigensolution with kinetic
energy and effective mass using checka.v68.  Note:  This run
generates "assembly plots" that include the "skeleton" of the
component transferred.

alter9g1.dat - Restart from alter3g1, perform modal transient solution.

Three additional files (se1g.dat, se2g.dat, se9g.dat) are available but
are not included.  These three files represent the workshop phase in
the second reference document.


Additional Documentation

R. R. Craig and M. C. C. Bampton, "Coupling of Substructures for
Dynamic Analysis," AIAA Journal, Vol. 6, No. 7, July 1968.

"Component Modal Synthesis for Coupled Dynamic Analysis Using
Superelements," MSC Internal Paper, June 25, 1992.