dolfin team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxx>]

I've added a strain reconstruction procedure to the elasticity demo. I'm
currently working on a plasticity demo, which will illustrate the
necessary steps for rather generic nonlinear constitutive models (stress
update algorithm, history variables, consistent tangent, etc).

Garth

On Fri, 2006-02-17 at 11:12 +0000, Alexander Jarosch wrote:
> Thanks Garth, exactly what I need, I want to calculate the strain rates 
> and out of that the stress tensor.
> 
> Alex
> 
> Garth N. Wells wrote:
> 
> >If you'd like to compute the gradient for post-processing purposes, you
> >need to set up a separate variational problem which would return the
> >gradient. Dealing with the gradient of a vector is a little tricky since
> >FFC and DOLFIN are not yet equipped to deal with tensor functions. Below
> >is an example FFC input file which would be useful for post-processing.
> >I'll add it to src/demo/pde/elasticity shortly. If you want to compute a
> >stress tensor from the strain, you'd probably want to make the elementE
> >"Discontinuous vector Lagrange".
> >
> >Garth
> >
> ># Compute normal strain components
> >#
> >elementE = FiniteElement("Vector Lagrange", "triangle", 1, 3)
> >elementU = FiniteElement("Vector Lagrange", "triangle", 2)
> >
> >v = BasisFunction(elementE)  # test function
> >e = BasisFunction(elementE)  # strain (to be computed)
> >u = Function(elementU)       # displacement 
> >
> >def normal_strain(u): # eps_xx    eps_yy             gam_xy
> >	return [u[0].dx(0), u[1].dx(1), (u[0].dx(1) + u[1].dx(0))]
> >
> >a = dot(v, e)*dx
> >L = dot(v, normal_strain(u))*dx
> >
> >
> >On Fri, 2006-02-17 at 10:03 +0000, Alexander Jarosch wrote:
> >  
> >
> >>Hello everybody,
> >>
> >>I am new to this mailing list and also new to the dolfin project. I 
> >>started to play around with the Stokes solver and have to say dolfin is 
> >>really neat to use, great job.
> >>I have a question, is there already a function to calculate the gradient 
> >>of the velocity field?
> >>
> >>regards,
> >>Alex.
> >>    
> >>
> >
> >
> >
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> >  
> >
> 
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-- 
Dr. Garth N. Wells
Faculty of Civil Engineering and Geosciences
Delft University of Technology
Stevinweg 1
2628 CN Delft
The Netherlands

tel.     +31 15 278 7922
fax.     +31 15 278 6383
e-mail   g.n.wells@xxxxxxxxxx
url      http://www.mechanics.citg.tudelft.nl/~garth