Reading or ignoring CBUSH elements from OP2

[Philip Moseley]

Hello Steve,

I've got a model with CBUSH elements, i.e.:

PBUSH    28      K       500000.2500000.2500000.

                 RCV     1.      1.      1.      1.

CBUSH   19925366 28     3565342835653429                         352

         .5

I'm running with MSC 2021, and I'm unable to read the Nastran OP2 file using read_op2 with load_geometry=True. I get the following error:

failed reading b'EPT' isubtable=-5

Traceback (most recent call last):

  File "D:\DATA_SLOW\TOOLS\FATIGUE_CALCULATOR\python-3.7.7.amd64\lib\site-packages\pynastran-1.4.0+dev.76717dbf9-py3.7.egg\pyNastran\op2\tables\geom\geom2.py", line 1802, in _read_dual_card

    n, elements = msc_read(data, n0)

  File "D:\DATA_SLOW\TOOLS\FATIGUE_CALCULATOR\python-3.7.7.amd64\lib\site-packages\pynastran-1.4.0+dev.76717dbf9-py3.7.egg\pyNastran\op2\tables\geom\ept.py", line 1369, in _read_pbush_msc

    assert ndata % ntotal == 0, f'table={self.table_name} leftover = {ndata} % {ntotal} = {ndata % ntotal}'

AssertionError: table=b'EPT' leftover = 648 % 92 = 4

Digging in, I see the comments in ept.py say new CBUSH elements aren't supported:

    def _read_pbush(self, data: bytes, n: int) -> int:

        """

        The PBUSH card is different between MSC and NX Nastran.

        DMAP NX 11

        ----------

        NX has 23 fields in NX 11 (supported)

        NX has 18 fields in the pre-2001 format (supported)

        DMAP MSC 2005

        -------------

        MSC has 23 fields in 2005 (supported)

        MSC has 18 fields in the pre-2001 format (supported)

        DMAP MSC 2016

        -------------

        TODO: MSC has 24 fields in 2016.1 (not supported)

        MSC has 18 fields in the pre-2001 format (supported)

        """

FYI, MSC 2021 has 27 fields now. Is there a way to skip this geometry? Or another workaround? I don't care about the CBUSH elements, but I need the rest of the geometry.

I could send some example files from MSC 2021 if it helps.

Thanks,

Philip

[steve]

It looks like they changed it in MSC 2021.  If you have a small example, I can add support for it.

You can skip the PBUSH by deleting the map to the function (so the passer gets called):

model = OP2Geom()

del model._ept_map[(1402,14,37)]   # (1402,14,37) is the PBUSH flag in the DMAP guide

model.read_op2(op2_filename)

If that doesn't work :), try:

model = OP2Geom()

model._ept_map[(1402,14,37)] : ['PBUSH', model._read_fake]

model.read_op2(op2_filename)

[Philip Moseley]

I've attached a small CBUSH example that runs with Nastran 2021.

I quickly checked the "del model._ept_map[(1402,14,37)]", looks very interesting. First challenge is that the OP2Geom.read_op2() command doesn't cover all the same parameters as the read_op2() does (notably for me, the "exclude_results"). Seems like it would be an easy fix though, since the read_op2_geom() function does support it, just copy the same commands?

Thanks for your help!

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[Steven Doyle]

Thank you for that.  Could you also take a screenshot of the DMAP guide PBUSH page?  It should look similar to this:

Regarding the include/exclude results, you can call:

    model.include_exclude_results(exclude_results=exclude_results,
                                  include_results=include_results)

To view this discussion on the web visit https://groups.google.com/d/msgid/pynastran-discuss/CAKhG9Z2nXePCiazj4VLDRNBrn2uG2c-Zkf_8jQwZ%2BTx_7SzWEA%40mail.gmail.com.

[Steven Doyle]

Oh and I guess while you're at it, can you take some pictures of the QRG and DMAP guide for the RBE3.  It changed.

[Cean Wang]

Where is OP2Geom() defined?

 

Sent from Mail for Windows

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