Plot Strain Energy Error Siemens NX 2

[Joao Gaspar]

Dear all,

I am new to Nastran, and I am currently performing a static analysis using Siemens NX 11 (SOL 101).
The Analysis Quality Report states strain energy error around 20%. With the goal of decreasing this value, I would like to know if is there any way to plot the strain energy error to refine the mesh where needed. I have looked already in the Output requests but couldn't find such parameter.

Thank you!

Br,
Joao

 

[simaonobrega]

In the Simulation Navigator, go to your ".sim" and create a New Solution Process - Adaptivity. Then select your Solution and set your Maximum Number of Iterations to 0.

 

[BlasMolero]

Dear Joao,
For meshing the important is the mesh quality, the quality of the elements of your mesh, terms like ASPECT RATIO, JACOBIAN CHECK, SKEW ANGLE, ALTERNATE TAPER, etc.. check your quality mesh.
Also, try to avoid using triangular 3-nodes or tetrahedral elements, instead use quadrilateral 4-node elements like CQUAD4 or hexahedral 3-D solid 8-node elements, these elements are more accurate.
Also, the element size is important, you need to create refined mesh to reduce the error of the discretization and obtain accurate stress results.
And finally the strain energy of the model:
In the NASTRAN Output Request you can ask to compute the STRAIN ENERGY (it will write ESE(PLOT) = ALL in the case control of the nastran input file *.dat):

After solving your linear static analysis then plot the results value of say STRAIN ENERGY PERCENT, the element strain energy output is an excellent tool for identifying areas of modification that will reap the most benefits for design changes (the element strain energy is basically the elastic energy stored in the structural element). And also is the location where surely your maximum stress is located, then do your best to mesh this area with quality elements, OK?

In the following image elements with no strain energy results are hidden: this information helps you identify areas of your model that can be perfectly neglected, not working at all.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
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Blog de FEMAP & NX Nastran:

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[Joao Gaspar]

Dear community, thank you for your feedback! It is always amazing how much we can learn at Eng-Tips.

simaonobrega, that is precisely the data I was trying to obtain. Thanks!

Blas Molero, thank you for the detailed information which will definitely help in decreasing the error that I am obtaining. I agree and understand all your statements, nevertheless, I was obtaining a strain energy error around 20%, even when using just CQUAD and HEX elements (quality within the acceptable parameters). Not understanding where the problem was, I decided to evaluate the energy error over my whole domain. Don't you consider such parameter in your analysis?

Kind regards,
Joao