On Wed, 30 Mar 2016, David Knezevic wrote: > P.S. Actually, there's also another issue that I think is more significant. > In order to implement radial return according to the algorithm in Simo & > Hughes, I store material data (e.g. plastic strain) at each quadrature > point "qp". But the finite difference jacobian does solves at "qp + h" , > and when it does those perturbed solves it uses the material data from > "qp", which is not correct. > > Based on my tests, I believe this is the real source of the mismatch > between the f.d. and analytical jacobian. (The effect I mentioned in my > previous email may be an issue too, but I think it's less significant.)
That would do it. If you want to do FEMSystem finite differencing on a moving mesh, and you don't use the ALE infrastructure, it's not going to be correct because the perturbations of your mesh position won't actually move your mesh. (of course, if you *do* use the ALE infrastructure, it's not going to be correct because I never got that solid and haven't had a chance to touch it in years...) --- Roy ------------------------------------------------------------------------------ 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 Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
