syfi team mailing list archive

[Harish Narayanan <harish.mlists@xxxxxxxxx>]

kent-and@xxxxxxxxx wrote:
> The nonlinear hyper-elasticity demos do not seem to produce
> the correct solution. I have been looking in particular on the Fung stuff.
> 
> Newton seems to converge with quadratic convergence whenever
> it is close to the solution so I think the differentiation is correct.

OK. I have been trying a few things over the past week (compiling forms
with FFC instead) and here is what I see:

1. Nonlinear scalar Poisson works.
2. Linear elasticity posed as a special case of a nonlinear problem
works. (Converges in one iteration).
3. Nonlinear elasticity (hyperelasticity with the St. Venant-Kirchhoff
model) a. does not converge or b. the direct solvers complain about a
singular matrix.

I didn't think to look into the boundary conditions for 3 because I used
the same setting as 2. I will look at them more closely.

Harish