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op2, f06 and displacements



I am trying to understand fully a point: NASTRAN writes GRID output to the CD (outcsys in FEMAP), both in the f06 and the op2. However for displacements if you import the op2 in FEMAP the output is not the same (RMS is, but components are projected in CSys0).


At some point a vector transformation is done. The MSC NASTRAN support tells me it's FEMAP (i.e. results in the op2 are written in the output CSys). If that is the case where does FEMAP find the transformation info? In the op2 or in the model?  


Is there other output for which there is a hidden transformation?


Is this documented somewhere? In Section "Selecting Data for a Deformed or Contour Style" it is explained that "FEMAP does not know, nor keep track of the coordinate system where your output is defined". Is displacement an exception when importing then?


Thanks for your help


Re: op2, f06 and displacements

To check further, I have always used PARAM POST -1 with FEMAP.

With PARAM POST -1 there is supposedly only one data block in the op2: OUGV1 which gives diplacements in the output CSys. The other existing datablock is OUGV1PAT which is in CSys0.


Do you confirm that POST -2 is not compatible with FEMAP? Which block does FEMAP read? Is there a transformation after the data is read?


Thank you

Re: op2, f06 and displacements

Femap is expecting an op2 file created with PARAM,POST,-1. This outputs displacements in the CD(Nastran Global) system. Femap uses the information contained in the modfem to determine if nodes have an output coordinate system and then uses this info to transform the op2 displacements into basic(system 0) before storing in the modfem.

You can then set Femap to display this data in any system defined in the model.

Re: op2, f06 and displacements

OK thanks for the info.

Is there any other output which FEMAP transforms when importing or is displacement strictly the only one?

Re: op2, f06 and displacements

Displacement data is the only one, element data is read "as is" then transformed on the fly as requested by the user.

Accepted by topic author astrium_tls
‎08-26-2015 04:32 AM

Re: op2, f06 and displacements

Actually I need to correct that to say we transform only  "nodal vector data" . So data like constraints forces also gets transformed.

Re: op2, f06 and displacements

What about Csys trasformation when Frequency Responce (Sine, Random, ...) Solutions results are loaded in FEMAP ? i.e. using DISP(...,PSDF) = ALL and PARAM,POST,-1.

Thank You