Modelling of Inflatable Beam Using Ansys

[mechie123]

Hello,

I have designed a mathematical model (theoritically) for an inflatable beam which comprises of internal pressure 4.5 Psi. One side of the beam is hinged and the other is simply supported. The specifics of the beam are:
Length : 1820mm
Diameter: 430mm
Thickness: 25mm
Internal Pressure:4.5 Psi
Material: Nylon
Internal Fluid: Air

Now, I have to validate my theoritical model by doing the same with ansys and compare the two results. Im unable to model the Inflatable beam in Ansys. Please help me with the modelling in ansys and to input properties of air inside the beam.

 

[prex]

As far as I can see, there are two effects related to your problem:
- the change in volume due to any deformation under load that's going to change gas pressure
- the tensile stress induced by pressure in the walls that's going to set farther away the local or global buckling of walls
The first effect is a non linear one and would require an analysis with the deflection related stresses turned on, but I don't think it is particularly important, at least for reasonable deflections.
The second one can be accounted for by superposing the known stress distribution due to pressure to the distribution due to other loads and using the resulting stresses to check for buckling.
Am I missing something?

prex

http://www.xcalcs.com

: Online engineering calculations

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[mechie123]

Prex,

U are right! after a certain limit of loading, the behavior of the beam tends to become non-linear, that's the point where the beam starts to 'wrinkle'(total non-linear behavior) . Though all that can be obtained mathematically, modelling it numerically is being a challenge! Your response is perfect, it behaves like the way you've mentioned. Any views with regard to numerical modelling?

 

[prex]

You could represent the gas as a solid with a Young's modulus equal to 3 times the bulk modulus, a Poisson's ratio of zero and a shear modulus as close as possible to zero. And of course you need a run with geometric non linearities turned on.

prex

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes and launchers for fun rides

http://www.levitans.com

: Air bearing pads