dolfin team mailing list archive

["Johan Hoffman" <jhoffman@xxxxxxxxxx>]

Sounds interesting! We will probably need some more postprocessing for the
modules ahead. I guess the functional output for FFC/DOLFIN is stuck with
me, and unfortunately I won't be able to do anything about that until
after Geilo in mid March.

/Johan


> 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
>
>
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