Retrieving Data from multiple results files based on Load Step and Substep in PyMAPDL

[ncbhatt]

Dear PyAnsys Team,

I’m currently working with .rst files using PyMAPDL to extract specific results based on load step and substep numbers. My simulation setup involves multiple load steps with several substeps, and I need to retrieve data precisely from specific substeps within these load steps.

However, when I attempt to parse the result sets using result.parse_step_substep(), I receive only integer indices representing the result sets, rather than a tuple containing the actual load step and substep numbers. For example, my .rst file shows 3 result sets, but the step info returned is simply 0, 1, and 2, without any clear mapping to the original load step and substep numbers from the simulation.

Given this, I have two questions:

1. Is there a current method within PyMAPDL to directly retrieve data based on specific load step and substep numbers (e.g., Load Step 3, Substep 5), rather than relying on the result set indices?
2. If this functionality is not currently available, could this feature be added or modified in future releases to allow users to access results based on their original load step and substep definitions in ANSYS? This would be incredibly helpful for simulations with complex step sequences.

Thank you for your assistance and support.

Best regards,
NC

[RobPasMue]

Hi @ncbhatt - let me move the discussion to PyMAPDL. Pinging also @ansys/pymapdl-maintainers for assistance

[ncbhatt]

Thank you very much.

[mikerife]

Hi @ncbhatt
This is a little confusing but the functionality you are asking about is the PyMAPDL Reader and not PyMAPDL. For better or worse the reader is packaged with PyMAPDL but it works differently. If you review its documentation the parse_step_substep returns a ccumulative list.

For a better post processing experience with this I would suggest using PyMAPDL and taking advantage of the enhanced output formats discussed here near the bottom of the page. Say I had a two load step solution and saved just the last substep of the first solve, and all the substeps of the second. Then using the SET command to list the available load/sub/result sets dumped to a dataframe would look something like this:

You can use the other enriched output types and see how they align with the listing information. Then parse the list/array as needed.

Mike

[ncbhatt]

Hi @mikerife,
I am absolute beginner for PyANSYS (having expertise in ANSYS MAPDL and basic knowledge of Python), so was not knowing that the functionality I was seeking is related to the PyMAPDL Reader, not PyMAPDL itself. Thanks for the clarification.
I am having 8-10 rst/rth files of same model (i.e. mesh/node number etc are same) in which different type of load cases are there (e.g. steady state thermal, structural, transient, creep etc) I want to extract data from all these files for a single node number. I dont want any display, I want values. Please inform, if pyMAPDL reader will be the correct option for me. Thanks in advance.
Regards

[mikerife]

Hi @ncbhatt
You may want to look at the nlhist MAPDL command. It can write node or element results, for a small set of either, to a file during the solution. If you want just some result at only 1 node then it may be more efficient to use than post processing.

What nodal data do you want? Knowing that may change my answer with respect to PyMAPDL vs PyMAPDL Reader...and nlhist!

MIke

[ncbhatt]

Hi @mikerife,
Thanks for your response and the information. My aim is to get stress/strain/temperature values from different rst/rth files for a same node number. These values should be stored in variables. The different rst/rth files contain steady state thermal, structural, transient thermal/structural and creep analysis for the same component (and same mesh). This extracted data will be used in an internally developed software for crack growth under creep-fatigue loading. Till now we are doing this data extraction manually. We want to automate it to cut the time.
Regards
NC

[mikerife]

Hi @ncbhatt
Well in that case you can use either PyMAPDL or the PyMAPDL Reader. Most, if not all, of the PyMAPDL Reader node result methods accept a load/sub step number as a list (rnum field).

In the future it may be better to have MAPDL write out the result(s) to a file after the solution. If you need a small example to get started let me know which version of MAPDL you use and the element type(s) used in the model.

Mike

[ncbhatt]

Hi @mikerife
having some example will be very much useful. Based on our conversation, I would like to use PyMAPDL Reader.
The elements I am using is plane77 (with axisymmetric option) for thermal analysis and plane 183 (axisymmetric) for structural analysis (in ANSYS).
Please look at the figure attached. I want to provide path for all my rth/rst files and respective load/substep numbers for which I want to extract data. On pressing confirm a popup will ask for node number and desired data (temperature/stress/strain/creep strain) for that node number should be there in the output column from all these files (that's the wish). First row data (temperature from a rth file for steady state thermal run) I was able to extract. Got stuck in the second row where I want von Mieses stress from a steady state structural run.

Regards

[ncbhatt]

I am using latest version of pyANSYS

[mikerife]

Which version of MAPDL?

[ncbhatt]

Sorry for a late reply. it is 2022 R2

[ncbhatt]

I created a repository. Whatever I did is here

https://github.com/ncbhatt/ANSYS-Data-Extractor?tab=readme-ov-file