ASME VIII D2 Elastic Plastic Analysis 1

[nashki]

Dear Community,

I am working on the elastic plastic analysis of ASME Section VIII Division 2 Part 5.

The material is SA-285 Gr. C, the Design Pressure is 0.3MPa at Design Temperature 200degC.

I use the ANSYS 2024 R1 for the analysis.

The material model with true stress-strain curve has been added as per Annex 3-D into the Multilinear Isotropic Hardening.

The large displacement for non-linear geometry is activated.

The load combination with design margin also been applied as per Table 5.5.

If refer to ASME PTB-3, Figure E5.2.3.2, it present the result of Von-Mises stress and Equivalent Plastic Strain.

And Figure E5.2.3.3, it is showing the Pressure vs Displacement.

Question:
What is the acceptance criteria for this analysis? Since the ASME only says "if the convergence is achieved, the component is stable under the applied loads".

How do we know if the analysis is convergence?

What would happen if the analysis is not convergence?

What is the applicable result to be showing in the report?

Shall we plot the result in the True Stress-Strain curve?

I have seen the several thread for this topic, but still didn't get the clear answer.

Thank you.

 

[IdanPV]

I had the exact same questions when I started to learn this topic.
See here:

https://www.eng-tips.com/viewthread.cfm?qid=457147

 

[nashki]

IdanPV,

Thank you for sharing the link.

I have read your topic before.

What would happen if the convergence is not achieved?

Does the analysis get error or what?

 

[IdanPV]

I don't know how it works in ANSYS but my software gives a solution error and analysis stops.

 

[nashki]

IdanPV,

What software do you use?

What is the root cause of the error?

Is that because the very high load, and the stress or strain result is beyond the material model curve?

 

[TGS4]

It doesn’t matter the root cause of the error. If a statically-permissible solution is not achieved, then you don’t have convergence.

 

[IdanPV]

It is recommended to take a look at AB-520 which provides information regarding the use of FEA in to support a pressure vessel design.
It also provide guidelines on how the report should look like, and what shall be included.

https://www.absa.ca/media/1210/ab-520-finite-element-analysis-fea-requirements.pdf

 

[nashki]

TGS4,
Understood, Sir.
Are you planning to have a course near South East Asia?
Canada is far away from my location.

IdanPV,
Appreciate for sharing the reference.

 

[r6155]

Why is ASME VIII-2 used for 0.3 Mpa?
What is the problem if ASME VIII -1 is used?

Regards

 

[nashki]

Hi r6155,

The vessel is in-service, not a brand new.

The client requires to perform the analysis per API 579-1, Annex 2-D, Elastic-Plastic Method.

 

[r6155]

@ ikhsani
Please
1) You mention a client.
What is your position?: consulting?,...?
2) What is the problem with the pressure vessel?

Regards

 

[nashki]

Hi r6155,

1. Yes, I am an Engineer, working in consulting.
2. The vessel to be re-evaluated using FFS-1, Annex 2-D.