Learning Forum

[cuppajoe]

Hey everyone, help would be greatly appreciated as I've been at this for days now and cannot locate my error!

I'm running a coupled thermo-structural analysis on a symmetric pressure vessel that has an internal pressure load as well as an imported body temperature load from a transient thermal analysis. The transient thermal analysis ran without issue and I had no problem imported the body temperature at the specific time I wanted to investigate into static structural.

However, the results of the structural analysis haven't been making any sense because they are showing that the highest hoop stress is on the outside of the pressure vessel instead of the inside where they should be and it's driving me crazy. The thing is though, when I run the simulation without any thermal load I get results that match up fairly well with thick walled cylinder equations.

Any help figuring this out would be awesome. Thanks!

[peteroznewman]

I'm interested in thermoelastic stress analysis. If you can share your project, please create an archive and attach the .wbpz file to your reply and say what version of ANSYS you are using.
If you can't share it, can you provide more information so I can recreate a similar model. What is the internal pressure? What is the material? What is the outside diameter and wall thickness of the vessel?

[cuppajoe]

Hey thanks for the response!
The wall thickness is 3/8 inch and the internal radius is 29.5mm. The cylinder is fixed at one end and open at the other and hot gas flows through it at a pressure of 1700psi. The material is 316 stainless steel. I'm still playing around with changing parameters and no luck. When I solve analytically, I come up with a similar situation where stress increases as radial position increases, which I think must be due to the temperature gradient. However, my analytical solution is much much higher than what I am getting in FEA. Analytically it shows that max stress (combined hoop stress due to pressure and due to thermal gradient) is nearly 1000MPa, whereas FEA shows max stress as somewhere around 300MPa. Any insights are much appreciated!

[cuppajoe]

[peteroznewman]

I built an Axisymmetric model. I didn't fix the end to make it a bit simpler to compare with analytical.
Here is the hoop stress for pressure only:
For temperature only, here is the hoop stress:
Here is the hoop stress for the combined loading:

[sreejith.sreedharan]

Hi, Peteroznewman, 

Can you tell me how to calculate the strain in hoop and radial direction for the above problem? 

I am trying to calculate these strains separately for thermal and pressure and for combined loading.

Thanks and regards

Sreejith