[CIG-SHORT] Principal Stress Axes

[Brad Aagaard]

On 4/9/13 8:27 AM, BOK10 at pitt.edu wrote:
> Thanks for the quick reply! One last thing. I just want to check that the
> negative Sxx/Syy values are compression and the positive tension?

Yes, negative axial stress is compression, positive axial stress is tension.

Brad

>
> Bobby
>
>> Bobby,
>>
>> Your best option is to write out to HDF5 files and use a Python script
>> to compute the principal stress axes. The PyLith binary includes the
>> Python h5py module which makes reading HDF5 files trivial. You can add
>> the principal stress values to the binary and then update the Xdmf file
>> using pylith_genxdmf. This will allow you to load the principal stress
>> values ParaView. See examples/2d/subduction/afterslip_tractions.py for
>> an example of reading an HDF5 file using Python.
>>
>> The stress coordinate system is the global XYZ coordinate system.
>>
>> Brad
>>
>> On 4/8/13 10:02 PM, BOK10 at pitt.edu wrote:
>>> Hi,
>>>
>>> I've been trying to take the stress output (Sxx, Syy, Sxy) and convert
>>> them to principal stress values and solve for the orientation of S1 in
>>> the
>>> global coordinate system. Is there a way to do this in Paraview? Also,
>>> does the stress output (vtk) write as a local system with the origin in
>>> the centroid of each cell with the x-axis parallel to the vector from
>>> the
>>> first node to the next, or is the vtk output based on cartesian x/y
>>> directions in my model? My model is a 2D model of strike-slip faults.
>>>
>>> I've been calculating the cell centers and exporting the cell data to
>>> excel to calculate the orientation of S1. This has been rather tedious
>>> considering the limitations of excel. Any insight in how to do this in
>>> Paraview, or if what I have been doing so far is on the right track
>>> would
>>> be greatly appreciated.
>>>
>>> Bobby
>>>
>>>
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>>
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