SIF calculation using FEA

I have a slanted connection in one of my calculations where I converted it using FEA Tools. Out of curiosity, I modelled the exact same connection in both FEPipe and NozzlePro as well. to my surprise, there is no similarity in the calculated SIF and flexibilities! can anyone think of any reasonable explanations?

Hi Pooria,

Did you use ASME B31.J in FEA Tools?

Warm Regards,

Hi Borzki,

I did! I am just not sure if using B31J for a lateral connection would do justice in obtaining the accurate SIF and flexibility values. my issue is the sif and flexibility values calculated by FEA tools are not in a par with similar variables but using FEPIPE or NozzlePro (and even the results from the latter two are not the same!)

Pooria,

Rerun your FEATools run, but select the "FEA" option.

The B31J option uses the empirical equations published in the ASME B31J Standard. Empirical equations are approximate, FEA will get you closer to reality. FEPIPE and NozzlePRO employ FEA methods, therefore depending on the parameters of your model, B31J may or may not agree.

Richard nailed it.

Sometimes, even FEA can have a slight difference with each other due to mesh sensitivity at the junction especially if singularity comes into play. Just make sure all the necessary settings are the same if comparing the results between two FEA run (mesh size, mesh type, boundary conditions, load application, geometry, thickness etc.).

Cheers!!

Richard and Borzki; many thanks for responding,

I think I may have caused a terrible misunderstanding! I used FEA conversion while using FEA tools. by the first Borzki's response, I foolishly thought he was suggesting a rerun with B31J. that's why I replied that I wasn't sure if this would be of any help on figuring out a slanted connection SIF/flexibility properties.
FEA method has been used in all of my 3 calculations using FEAtools, FEPipe and NozzlePro. in all 3 programmes I have modeled the exact same slanted connection qua material, thickness, geometry, boundary and process conditions otherwise any comparison between the results of those 3 would be nonsensical.
By the way, I don't think the meshing settings in FEAtool and NozzlePro can be changed. if it can, can you please let me know where to access it in those softwares?

many thanks in advance,

What are the figures you are getting? Is there a large impact on calculated stress?

I would suggest to compare first the calculated stress instead of SIF's and flexibilities.

As always suggested, you can start from simple geometry, load and start your comparison from there and work all the way up.


Cheers!!

If you're manufacturing the connection by cutting 2 pipes and welding them together, then PRG software is likely telling you an accurate story.

However, I'll note that I wouldn't ordinarily recommend installing piping in this configuration, but to use a forged fitting, which looks substantially different.

Allegedly, those forged fittings's flexibilities and stiffnesses are comparable to that of a regular welding tee.

Edit to add: The PIP standard has some short discussion on the topic, though it's roughly as verbose as I am above.