[Paraview] Fwd: Question about strain from filter: Compute Derivatives -> Vector -> Strain.... type?

[Tim Bhatnagar]

Awesome! Thanks for the help, Andy!

Tim


On Thu, Mar 13, 2014 at 12:35 PM, Andy Bauer <andy.bauer at kitware.com> wrote:

> Hi Tim,
>
> The class that does that computation is called vtkCellDerivatives. It
> looks like the part of that code that does the strain computation is:
>           tens->SetComponent(0,0, derivs[0]);
>           tens->SetComponent(0,1, 0.5*(derivs[1]+derivs[3]));
>           tens->SetComponent(0,2, 0.5*(derivs[2]+derivs[6]));
>           tens->SetComponent(1,0, 0.5*(derivs[1]+derivs[3]));
>           tens->SetComponent(1,1, derivs[4]);
>           tens->SetComponent(1,2, 0.5*(derivs[5]+derivs[7]));
>           tens->SetComponent(2,0, 0.5*(derivs[2]+derivs[6]));
>           tens->SetComponent(2,1, 0.5*(derivs[5]+derivs[7]));
>           tens->SetComponent(2,2, derivs[8]);
>
> My suggestion would be to use one of the gradient filters (either Compute
> Derivatives or Gradient of Unstructured Data Sets) and then either use the
> Calculator filter (slower but simpler) or the Python Programmable filter
> (faster but more complicated) to compute your desired results.
>
> Regards,
> Andy
>
>
> On Thu, Mar 13, 2014 at 3:23 PM, Tim Bhatnagar <tim.bhatnagar at gmail.com>wrote:
>
>> Fair enough.... I'd like to think that since the infinitesimal strain
>> tensor is just a simplified version of the Green-Lagrange tensor (really,
>> some usually-small terms just get assumed to be zero), that the Paraview
>> designers utilized a fully-designed Green-Lagrange formulation, which will
>> approximate to the infinitesimal strain tensor then the strains are small...
>>
>> But it'd be great to get a definitive answer.. otherwise I ened to think
>> about creating my own filter to determine the finite strain tensor.
>>
>> Thanks for the comment,
>>
>> Tim
>>
>
>


-- 
Tim Bhatnagar
PhD Candidate
Orthopaedic Injury Biomechanics Group
Department of Mechanical Engineering
University of British Columbia

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