On Wed, Mar 30, 2016 at 9:11 AM, Paul T. Bauman <[email protected]> wrote:
> > > On Wed, Mar 30, 2016 at 8:00 AM, David Knezevic < > [email protected]> wrote: >> >> >> Thanks for your comments. The problem I'm considering is plasticity, >> using the radial return algorithm. As far as I can tell, the code matches >> the text book, and it converges correctly. However, it doesn't match the >> finite difference Jacobian from FEMSystem. So there are two possibilities: >> >> 1) Somehow the finite difference Jacobian is inconsistent with the radial >> return algorithm. This doesn't seem impossible to me, given that the radial >> return algorithm is highly path-dependent. >> > > This is very much a thing. What reference are you using? The Jacobian you > get from the equations vs. the Jacobian which includes the radial return > algorithm ("consistent tangent" as the community calls it) are different. > Simo and Hughes, "Computationally Inelasticity" has a good discussion of > this. > I'm using Simo and Hughes. I implemented the algorithm in "Box 3.2" of that book for radial return, and it seems to be working fine. However, I would have thought that I could use a finite difference Jacobian based on the residual that is given by the radial return algorithm (i.e. the residual that uses the stress from radial return). I would have thought that yields a "consistent tangent", no? David ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
