Pressurized cylinder with axial comprex load (BUCKLING)

[Ing.marco.soave]

Good moring to everybody!

I have some problems related to the topic... So... I have this cylinder:

Radius= 275mm
Lenght= 1000mm
(conseguentely a=1000,b=1727.85)
I've applied a comprex load of 536.64 N/mm accordingly with NASA SP-8007 with a knockdown factor of 5674 by Hypersizer in the FBD page. I've used an one stack unstiffned concept leaving not equal to zero only the top face of the panel in order to simulate a simple walled cylinder. Using the NASA-SP8007 method with all clamped edges i've obtained a thickness of 2.51 mm while with analythical method i've obtained 2.5 mm that is absolutely correct. Now i have to study the effect of internal pressure. The internal pressure makes a bigger buckling load due to interaction with the benefic effects of the same pressure. I don't understand why if i choose a pressure value in Hypersizer, the margin os safety does not change.

Is it possible that the pressure isn't taked into account? How can i resolve this question?

Thanks for all the answers!

[Ing.marco.soave]

Ok...after several example cases my question is more more more simple...Why panel pressure dosen't work with curved panels? Is there any options that can i check in order to work in this direction?

Thanks

[Ryan]

Superimposed panel pressure is for flat panels only.

Curved panels react pressure loads in the hoop direction.  Apply Ny load to model the effects of a pressurized cylinder.

The NASA SP-8007 method as implemented in HyperSizer supports uniaxial loads only.  The method also assumes the curved panel is a full cylinder. (SP-8007 Equation Number 37-43, Pages 16 and 17).

The Rayleigh-Ritz solution "Curved or Flat, All BC" is much more general.  It supports:
- biaxial loads and shear
- curved panels & full cylinders
- all boundary conditions

-Ryan

[Ing.marco.soave]

Thanks a lot for reply...

Marco