Pipe Effective Axial Force from the fluid inside the Pipe - how to include in solid FEA?

[EngineerMickeyMouse]

Greetings.

My question is in reference to the Effective Axial Force phenomena.
Please imagine pipeline constrained at the ends and loaded with internal pressure, with fluid inside.
From structural perspective, internal pressure, constraints and Poisson's ratio will effect in Tensile force in the pipe's wall.
From fluid mechanics perspective, upthrust of the fluid will effect in Compression force in the pipe's wall.
Superpositions of this forces will be always compression force, since Poisson's ratio for steel is 0.3 which is smaller than 0.5. If it would be larger, the force would be in tensile and there would not be danger of buckling.

It is obvious how to model in solid FEA pipe segment an internal pressure, but I have no idea how to include Compression force with fluid mechanics origin? Could you please advise, and please do not send me to CFD, since I would like to perform this in static linear analysis.

 

[BigInch]

Pressured pipe constrained at the ends is in axial tension, if there has been no temperature change. If heating at constant pressure has occurred, axial tension is at first reduced and, if heating continues, may introduce axial compressive stress into the pipeline. If the pipe is not restrained at its ends, this stress = 0

Compressed fluid within the pipe is resisted by ring tension, transverse to the pipe axis = PD/2/t

The third component is pressure p on the inside of the pipe wall, resisted by radial stress within the pipe wall. r = p

 

[EngineerMickeyMouse]

Thanks for response, however could you please clarify how this is answering my question? I cannot see it.

 

[BigInch]

Put the pressure load on the inside wall directed outward.

 

[dhengr]

EngineerMickeyMouse:
Pipe stresses due to internal fluid pressure has little to do with Poisson’s Ratio, at least at the first/basic level of calculating gross pipe stresses. It mostly has to do with understanding all of the loads on the pipe: be they pressure loads, axially (capped ends?) and/or w.r.t. a free body ring of pipe, radial and circumferential; pipe bending, btwn. supports for example; expansion and contraction due to temp. changes, if the lengths of pipe are really constrained, etc. Dig out some good Strength of Materials or Piping Design textbooks, and study some of the basics. If you haven’t done that it sounds pretty dangerous that you pretend to be using FEA for pipe design which could hurt someone. It sounds like you are confusing some second order stress factor that you have heard about as it relates to the basic stresses in the pipe.

 

[EngineerMickeyMouse]

You missed the point. However thanks for contribution.
If you would like to trace my question and seek for answer, please review the link which my question is refering to. Link

Dhengr, do not be afraid, strength of matrials school basics etc is long past behind me, however still used in everyday practice.

Could you please advise - looking at the link - what is the physical definition of effective force?
I think perhaps you have not get me correct.

My question is how to apply in FEA (recommended practice), load representing displaced fluid column in the pipeline?

Otherwise it might be that it is not aknowledged by you what dicplaced fluid column I am refering to. Please discuss, I will appreciate.

 

[rconner]

From a quick reading of this thread I believe that most learned responders have assumed when you said "constrained" that you really meant that (i.e. in effect the ends are somehow totally fixed in position, as opposed to perhaps a more common cases of a pipeline, branch, vessel or tank closed off with a plate or head, in effect really "restrained" as by weld etc. but that would have ability to change in at least length due to Bourdon or thermal effects etc).
[When I see the "0.5" mention in the OP, I fear you might actually instead have the latter situation where the blanked end of the pipe is free to move at least axially, as I really have no other explanation the "0.5" factor you state, other than otherwise unbalanced end thrust on a welded plate, head or otherwise unrestrained thrust focus etc.?]
All have a good weekend.

 

[IFRs]

Please explain with a sketch or diagram "From fluid mechanics perspective, upthrust of the fluid will effect in Compression force in the pipe's wall."

 

[EngineerMickeyMouse]

Please see, from the link I have provided in the 6th response. Well explaine, if in doubts kindly please refer to link, since the sotry is not short and not straight forward.

 

[prex]

EngineerMickeyMouse, as for most responders above, it is unclear to me what are you looking for.
Can you explain what is your actual poroblem in modeling? That is: what pipe, how supported and constrained, etc. Making reference to a paper that, believe me, uses somewhat obscure terms that are uncommon in piping structural analysis, does not help, we can't study in depth for you the content of the paper.
Also, some of your statements are quite obscure: if the fluid is inside the pipe, how can the internal pressure result in compressive axial forces? (apart from bending, but you don't state anything about bending). And what do you mean by comparing the Poisson's ratio to an otherwise undefined coefficient 0.5?
Normally you would put the actual pressure on the pipe wall, and FEM will calculate for you all the relevant effects. But of course, if your model is not complete (end caps, supports), you'll need to apply proper boundary conditions.

prex
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[EngineerMickeyMouse]

Thanks for contribution, I will response when I will have time, which unfortunatelly at the moment I do not have...