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cylindrical shell stresses

  • Thread starter Thread starter luigi.paiano
  • Start date Start date
uhm even if I think they are the constraints on the ends that preventing the shifts cause me deformations and so the stresses!! I will ask the teacher!
 
In my opinion the axial sigma is not there....the tube axially is subject to the actions of the existing tao because of the limit layer of the fluid and for this it is "maintained"....the axial sigma due to pressure I think there are no!
 
a fluid in a pipeline 3 energy components of kinetic, geodetic and pressure origin (see bernoulli). if a fluid crosses a duct will undoubtedly generate a push on the walls that is called pressure. I would like to remind you that rains are interrupted before the famous 10 meters to avoid that once completely full you have in the top (before 10 meters column of water) that unpleasant crushed tube effect that breaks the rain. It is worth noting that the pipe is open both on the roof and in the drain of the gravel.


then if the tube has the cap becomes a pressure vessel. .
 
but if we have to reason only on the fluid interaction walls then the pressure is radial and more because of the viscosity I have tangible actions.
If I have no constraints limiting axial movements from where axial deformations arise? ?
 
banal question. Do you get air in pressure in a straw? ? in part for viscous friction between fluid and parerti, not for the pressure of the compressor....urge 4 opinion from other user! ;)
 
the tube is not suspended in the vacuum and however even if it is placed on two bearing supports that allow free movement from the outside world regarding deformations if the pressure exists this act and moves in the fluid zone.

then since it is a pipeline tube, the cap or valve or reduction system section there is!

If you shoot air in a straw, it doesn't stretch as much as you'd get if you really had the pressure on your gun, i.e. 6 bars.

transforms the pressure into speed, expands and therefore the pressure is very low, therefore the straw is not long.

We need more advice.
 
meccanicamg said:
Is the pressure open?
Click to expand...
Yes, otherwise the fluid would not move... there is a difference of die.. is more correct
But I'm sorry. I'm doubtful. ..when the fluid is spotted there is the speech I make....poi at a time when the sistribuzione is interrupted... So there's axial sigma like mecc....uhmmm thor you say?? ? ?
 
cesius79 said:
Yes, otherwise the fluid would not move... there is a difference of die.. is more correct
Click to expand...
if there is a difference of pressure upstream and downstream, the tube is subject to the difference of pressure.

Clearly if I have a defined range at the entrance, I will have a pscession or better a lesser pressure difference if I have the open end than the stage. But if you say: in the tube there are 4 bars....that is.
 
the pressure that is meant is the relative one therefore stopped or not changes the difference of pressure but I do not think it is involved with our speeches
 
meccanicamg said:
if there is a difference of pressure upstream and downstream, the tube is subject to the difference of pressure.

Clearly if I have a defined range at the entrance, I will have a pscession or better a lesser pressure difference if I have the open end than the stage. But if you say: in the tube there are 4 bars....that is.
Click to expand...
I think it is so...cmq somewhere I had the sizing of pressure ducts...the reasoning that has been done together is right anyway...the tube is more stressed when you stop....we think for example to a dead dog that blocks it:wink:
At that point you have a conduct with a steady fluid and maximum pressure....ok mec convinced me:)
 
I'm an engineer. But students are always. You can never stop banging your head in these things
 
I agree. That's why the part of calculations, Luigi, you have to do it yourself... if you don't bang your head you don't learn!
and anyway the speech of the pressure I am convinced is just in case of steady flow... I remain the doubt you know? since then we have to put in the worst case(valve closing the conduit) then size with pmax... back?
 
Yes, at the closed valve you have pmax regardless of our vibrations on the plugs. It's already so much that you don't have to count on the air blow... even if the fatigue test is to be calculated.
 
I think you're losing a bit of view of the problem, because I've heard about the limit layer of the fluid, but if I don't remember bad in the problem we don't talk about fluid moving, so no limit layer. a fluid can exert pressure even if moving (at least theoretically), then tau stem from the forces applied on the tube. the fact that it mentioned to the infinite tube is simply to eliminate any effects of edge that there would be in the case of a finished tube. the internal pressure of hydrostatic type, generates a plane state of stress, which implies the absence of axial tensions, due to pressure.
the axial stresses I would say that there are here, since the tube is subjected to bending moment.
the extension of the tube, if present, is due to the other forces or pairs agents and can result from sigma_z or tau_rz and tau_zteta.
to those who asked me why the use of equations in cylindrical coordinates, I answer saying that the choice of a coordinate system that fits better than another to the geometry of the problem is as important as the distinction of constraints and forces in play because it can greatly simplify life. Since the problem is cylindrical, I don't see why we should head towards using the Cartesian coordinates, when there are precisely the cylindrical polar coordinates that fit perfectly to the problem. Moreover many of the formulas found on the manuals derive from the proper solution of equations in cylindrical coordinates. an example calculate the polar moment of inertia j0 of a circular crown.
I do not deny that mine is a bit of a deformation as an aerospace engineer, that when he sees a shell subject to pressure he immediately imagines a fuselage, but I assure you that as much as they may seem antipathic, often the cylindrical polar coordinates are a great help.
 
thor105 said:
....
.
Click to expand...
noo thor should reread all the discussion.. we wondered if the pressure was considered as action that puts in traction the tube axially....and in fact the worst case is still fluid and therefore maximum pressure (closed valves or dead dog that blocks the conduct :biggrin:)
 
cesius79 said:
I agree. That's why the part of calculations, Luigi, you have to do it yourself... if you don't bang your head you don't learn!
and anyway the speech of the pressure I am convinced is just in case of steady flow... I remain the doubt you know? since then we have to put in the worst case(valve closing the conduit) then size with pmax... back?
Click to expand...
but look at that you are talking to one who makes the square bouquet every day and if known I never ask simple questions but at the most I look for opinions!!
However solved the mystery, we can consider longitudinal welding.
the welding is solicited (in the worst case, i.e. when located at distance r from the black axis) by bending + axial effort due to p in its cross section and by a perpendicular effort due to the circumferential one.all this if there is no torque moment,otherwise you must add the tangential effort in the longitudinal section of the welding
 

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