# Buckling of a simple cylinder with internal static pressure

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Good morning Mrs/Mr,

I downloaded ESAComp last week in order to study the buckling of simple structures during my internship with Arianegroup and have been struggling with one point.

I started with very simples cases such as steel or aluminium cylinders (1 layer, no composite) and the results in buckling are coherent with my theoretical expectations. However, when I started to add an internal static pressure to my cylinder, the results went wrong (RF_1= 0,01 for example). I have no idea how to simulate the buckling of a cylinder with a static internal pressure.

I used my previous cases of simple cylinders in steel or aluminium and filled in an external pressure in kPa in the tab for load parameters. Then, I ticked “Pressure Vessel” and ran the simulation.

Should I put a sign minus in front of the pressure to indicate ESAComp the pressure is internal? I tried and the RF_1 becomes negative.

Should I enter operation conditions ? I filled a min and max pressure (1 atm) and the results didn’t seem to change.

Is the pressure inside the cylinder static? If not, how can I simulate the buckling of a cylinder with a static internal pressure?

I didn’t find any tutorial or answer on the net nor on ESAComp examples. I hope you will be able to help me.

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Internal pressure generates tensile hoop stress for open cylinder and bi-axial in-plane tensile stress for closed cylinder. So it stabilizes the cylinder, it will not buckle. In ESAComp, internal pressure is defined as negative pressure. In the load specification, there is a check box for “pressure vessel” option. When checked, also axial load is set which mimics as the cylinder would be closed.

You have to notice that when you perform buckling analysis with load vector {F}, that always -1 x {F} is also considered. Let’s say that {F} represents internal pressure. In this case, there is no stability issue. But the eigen value problem is also solved with -1 x {F}, which corresponds to external pressure and then you have solution. In this case the load factor is indicated with negative sign.

If you want to consider the stabilization effect of the internal pressure in ESAComp, then you have to use geometrical nonlinear analysis.

Under the ESAComp program “Document” -folder, you’ll find ESAComp Example Cases.pdf. There are plenty of cylindrical shell related case studies. All related ESAComp projects are under Demo-cases.

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my comment is not related to that post , I just wanted to contact you but I was not able and the only way to do so is this comment about this recent post , so would you please walk me through the whole process of this video which is a beam subjected to a follower force , the owner of the video created a beam with RBE2 and nodes already defined then he applied that force , I just wanted to re-do the same thing with a Rod or even understand how he made it from the beginning , avoiding the importation of the file beam. thank you so much in advance

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