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Subject: Re: contact stiffness, convergence, and solution ti me.
Author: Bill Newland
Date: 2002-09-30 10:48:00

It's been a long time since I have done substructuring. Another limitation
of the frontal solver which was also the only solver available for the USE
pass was a limitation on the master degrees of freedom. I recall hitting
this limitation quickly with Contact52's in the USE pass interfacing solid
model portions defined as superelements.

I was under the impression that Substructuring had become somewhat obsolete
with the advent of Solid92's and new solvers, but now that the Sparse solver
can be utilized for the Substructuring technique - maybe this technique
should be re-evaluated as a possible method to reduce run time for solid
model assemblies interfaced with Contact170/174's.

I was wondering if anyone has had any recent Substructuring experience in
this regard.

Bill Newland
Bell Helicopter, Textron

-----Original Message-----
Sent: Friday, September 27, 2002 7:06 AM
To: 'xansys@yahoogroups.com'

Several years ago, I wrote a macro that would automatically substructure a
contact problem so that once the superelements were generated, you only had
to iterate on the contact elements. It wasn't very efficient because you
had to use the frontal solver for the generation pass, which was about 20x
slower than solving the entire model once with the PCG solver.

The latest version of ANSYS now lets you do superelement generation with the
sparse solver, so it might be worth trying this technique again.

Joe Metrisin
Florida Turbine Technologies, Inc.


My compliments to Don Shaffer on expounding the need of faster solution
time for detailed models with contact elements!

Thanks to CAD transfers, automatic tetrahedron element meshing, and contact
elements - we are finally able to model interconnecting machine components
as they really are. Now, if we could just do it without tying up our
computers for days.

One model I solved recently has about 800,000 dof's , 41 Contact 170/174
interface sets, and about 20,000 Contact 170/174 elements. I did get good
results - but it took 6 cpu DAYS on an SGI Octane. Substantial modeling work

was expended to get the model size down without deleting important detail.
While it is amazing that ANSYS can solve a problem like this at all, a much
faster turn around time is required in order to be practical.

Bill Newland
Bell Helicopter, Textron
Posts possibly associated with message #42300AuthorDateScore
42300Re: contact stiffness, convergence, and solution ti me.Bill Newland2002/09/30 
42309Re: contact stiffness, convergence, and solution ti me.Dan Bohlen2002/09/30 
42326Re: contact stiffness, convergence, and solution ti me.Sheldon Imaoka2002/10/01 
42343Re: contact stiffness, convergence, and solution ti me.Bill Newland2002/10/01 
42351Re: contact stiffness, convergence, and solution ti me.Sheldon Imaoka2002/10/01 
42364Re: contact stiffness, convergence, and solution ti me.Bill Bulat2002/10/01