BUCKLING ANALYSIS OF THIN-WALLED CYLINDER UNDER LOCAL RADIAL EXTERNAL FORCE AND EXTERNAL PRESSURE

[mechengineer]

Anyone can provide the formula or relative information for buckling analysis of thin-wall cylinder under loacal radial external force (Fex) and external pressure (Pex)? Thanks in advance.
As I know WRC107/297 for stresses analysis with internal pressure and external loadings only. I am not sure if FEA (NozzlePro) can do the buckling analysis or not.
If Pex/Pcr + Fex/Fcr <=1 is applicalbe for the buckling analysis? We can find 'Pcr' by external presuure calculation and 'Fcr' by Roark's formula.

 

[Ray6]

You can do FEA for buckling using Abacus or Ansys. I have not seen buckling calculation in Nozzle-pro.

 

[MJCronin]

There is no single formula for what you desire.

If you cannot find your formula in "Roark", it does not exist ...

MJCronin
Sr. Process Engineer

 

[saplanti]

mechengineer,

As far as I know there is no off-the-shelf study on this type application. External pressure creates compression stresses on the cylindrical shell whick can end up with buckling ultimately, local radial load (you don't explain the application. Is it radial nozzle or plate attachment?) can introduce different directional stresses which depends on the application. Therefore the solution can be found by a complex FEA.

You need to be practical. The buckling can be prevented by circumferantial stiffening. In case the radial load application through a plate attachment, you can use two stiffeners to distribute the load as well as protect against buckling. In case the losd is through a pipe with shell opening you can still use two stiffeners against the buckling and provide some stiffness for the stability of the shell under nozzle load (in this scenario you may still need to use FEA to warranty stability of the shell in case the load is high).

Hope it helps.

 

[HTURKAK]

Anyone can provide the formula or relative information for buckling analysis of thin-wall cylinder under local radial external force (Fex) and external pressure (Pex)? Thanks in advance....

For the buckling of thin walled cylinders for radially acting forces , you may look to Theory of Elastic Stability (Timoshenko), Stabilitätsprobleme der Elastostatik-, Alf Pflüger (auth.)...

Regarding the local radial force, if it is a point load , you may look to APPLIED MATHEMATICS A N D MECHANICS ( B.Budiansky).

If the local is distributed , you may look AWWA M11 Steel Pipe - A Guide for Design and Installation.

The buckling pressure for acting radially uniform, is , qk= ( E/ 4*(1-v**2))*(t/R)**3

 

[r6155]

I do not believe that a local external radial force influences the resistance to external pressure buckling. You can calculate with the normal procedure for internal pressure vessel but changing the stress signs appropriately.

Regards

 

[r6155]

More informaton in PD 5500 2018

G.2.2.2.4 Effect of internal and external pressure
A conservative result is obtained for total stresses if the stresses due to the
pressure are simply added to those due to local radial loads calculated in this
clause.
This method cannot be used for vessels under external pressure because the
deflection due to the radial load always increases the out-of-roundness of the
shell. For the same reason it should not be applied to a cylindrical shell subject
to an axial compressive load as well as a radial load. In these cases the deflection
due to the radial load should be found as in G.2.2.4 and the effect there of
assessed in relation to shape requirements specified in 3.6 for such vessels.
Annex M is intended for use with deflections due to shape imperfections and
may not always be conservative with estimated deflections due to local loads.

Regards