Failed reading b'OSERT'

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Ionut Cosmin Oncescu

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Mar 11, 2021, 4:06:55 AMMar 11
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Hi, I am trying to read an op2 file with results from MSC Nastran 2017, and I am getting this error:

DEBUG:   op2.py:542                   combine=True
DEBUG:   op2.py:543                   -------- reading op2 with read_mode=1 (array sizing) --------
INFO:    op2_scalar.py:1556           op2_filename = 'launch.op2'
DEBUG:   op2_reader.py:270            mode = 'msc'
DEBUG:   op2_scalar.py:1735             table_name=b'GEOM1'
DEBUG:   op2_scalar.py:1735             table_name=b'GEOM2'
DEBUG:   op2_scalar.py:1735             table_name=b'GEOM3'
DEBUG:   op2_scalar.py:1735             table_name=b'GEOM4'
DEBUG:   op2_scalar.py:1735             table_name=b'EPT'
DEBUG:   op2_scalar.py:1735             table_name=b'MPT'
DEBUG:   op2_scalar.py:1735             table_name=b'OQG1'
DEBUG:   op2_scalar.py:1735             table_name=b'OES1C'
DEBUG:   op2_scalar.py:1735             table_name=b'OEFIT'
DEBUG:   op2_scalar.py:1735             table_name=b'OESRT'
ERROR:   subcase.py:528               STRESS/STRAIN
ERROR:   subcase.py:529               {'_encoding': 'utf8', 'load_as_h5': False, 'h5_file': None, 'size': 4, 'is_msc': True, 'is_nasa95': False, 'table_name': b'OESRT', 'approach_code': 14, 'isubcase': 1, 'table_code': 56, 'tCode': 56, 'sort_code': 0, 'sort_method': 1, 'device_code': 4, 'analysis_code': 1, 'sort_bits': [0, 0, 0], 'element_type': 95, 'load_set': 5, 'format_code': 1, 'num_wide': 9, 's_code': 0, 'thermal': 0, 'lsdvmn': 1, 'data_names': ['lsdvmn'], 'nonlinear_factor': nan, '_times_dtype': 'float32', 'thermal_bits': [0, 0, 0, 0, 0], 'element_name': 'QUAD4LC-composite', 'subtitle': 'OSL_101.SC1', 'subtitle_original': 'OSL_101.SC1', 'pval_step': '', 'superelement_adaptivity_index': '', 'label': 'SUBCASE 1', 'title': '', 'stress_bits': [0, 0, 0, 0, 0], 'is_stress_flag': True, 'is_strain_flag': False}
failed reading b'OESRT' isubtable=-4

It seems that it won't read my Stress/Strain data. What could be the cause of this?

Thanks.

Steven Doyle

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Mar 11, 2021, 11:12:36 AMMar 11
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Do you have an example?

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Ionut Cosmin Oncescu

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Mar 15, 2021, 9:47:19 AMMar 15
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Yes, I have attached an .op2 example that I am running with a composite plate. It seems the problem occurs when I am requesting Strength Ratio for composite Ply's (with PARAM SRCOMPS YES). The program can't read the "OESRT" table.

I looked online and the problem seems to be the fact that the Nastran failure index datablock (OEFIT) has the same format as the SR datablock. I tried using and alter that substitutes Failure Indices for SR values (from here: https://www.eng-tips.com/viewthread.cfm?qid=451430 )

If I comment the strength ratio output, everything works fine.
TestStressTemp.zip

Steven Doyle

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Mar 16, 2021, 1:53:44 PMMar 16
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If you just want to skip the results, you can use the dev branch.

Can you also attach the bdf and f06 that goes with this?  The OESRT table is a little weird.  I think it has mixed types (sometimes a field is an integer and sometimes a float) and it's undocumented in the dmap guide.  


Ionut Cosmin Oncescu

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Mar 17, 2021, 2:57:23 AMMar 17
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I have attached the bdf and f06 files in a zip archive.

I don't want to skip the strength ratio results. Until now I was reading them from the f06 file with a python script that I made and was looking to see if I can read them from .op2 with pyNastran.

Thanks!
testTempStress_bdf_f06.zip

Steven Doyle

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Mar 19, 2021, 2:25:48 AMMar 19
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Give the latest version a shot.  It's not vectorized yet, but it should work for ctria3s, cquad4s, ctria6s, and cquad8s.  Run the following to see the new outputs:
>>> test_op2 testTempStress.op2
Off the top of my head, I believe you want model.op2_results.strength_ratio.cquad4_composite_stress.  Not 100%, but it should be similar.

The key outputs are self.data (the 3 float values: sr_bonding, fi_bonding, and sr_bonding), failure_theory_flag, which are strings (2 columns) and element_layer, which is the same as the composite stress/strain results.  The write_f06 method is supported as well.

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