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Subject: Re: UPF: Is an unsymmetric consistent tangent possible?
Author: Grama Bhashyam
Date: 1999-01-13 15:58:00

As my colleague Charles Rajakumar replied, ANSYS supports
> unsymmetric equation solution. ANSYS Newton-Raphson
> scheme does not depend on symmetry.

> There are elements such as 181, which provide a unsymmetric
> element matrix due to follower load effects.

> However, unsymmetrix material tangent matrix implies a unsymmetric
> material stiffness (B^T D B, where D is unsymmetric). Currently,
> ANSYS element library assumes symmetric material stiffness.
> There are other factors such as condensation of extra shapes,
> which also assume symmetry. We will address this limitation
> in a future release.

> User element is the only applicable option currently.

> Grama Bhashyam
> Mechanics Group
> ANSYS Inc.

> -----Original Message-----
> From: Frank Rackwitz [SMTP:Frank.Rackwitz@T...]
> Sent: Wednesday, January 13, 1999 9:51 AM
> To: xansys-Maillist
> Subject: [xansys] UPF: Is an unsymmetric consistent tangent
> possible?

> From: Frank Rackwitz

> Dear all,

> First of all - best wishes to the new year for all subscribers of
> xansys@o...
> This is my problem:
> I use the UPF-subroutine "userpl.f" in ANSYS 5.4 for implementing the
> elasto-plastic law based on the Mohr-Coulomb yield criterion with
> nonassociativ flow rule. This routine produce an unsymmetric
> consistent
> tangent matrix.

> Is it possible to solve this unsymmetric matrix with Newton-Raphson
> iteration scheme ???

> I read at the ANSYS Theory Reference, 4.1.7, following: "...To
> preserve
> the symmetry of the matrix, for analyses with a nonassociative flow
> rule, the matrix is evaluated using F only and again with Q only and
> the
> two matrices averaged."

> Thanks, Frank Rackwitz.

> Dipl.-Ing. Frank Rackwitz
> Technical University of Berlin
> Institute of Geotechnical Engineering
> Sekr. B7
> Strasse des 17. Juni 135
> D-10623 Berlin
> GERMANY

> EMAIL Frank.Rackwitz@T...
> PHONE +49-30-314-22861
> FAX +49-30-314-24492

Posts possibly associated with message #203AuthorDateScore
198UPF: Is an unsymmetric consistent tangent possible?Frank Rackwitz Frank.Rackwitz@1999/01/13 
202Re: UPF: Is an unsymmetric consistent tangent possible?Charles Rajakumar1999/01/13 
203Re: UPF: Is an unsymmetric consistent tangent possible?Grama Bhashyam1999/01/13