air pressure as radially acting loads?

Dear all,

I noticed that a half sphere-mesh will changing its curvature after inflated.

I assuming that Kangaoo-Pressure works as radially acting loads, and the result of final curvature should, theoretically, as a sphere/circle.

But I could be wrong, coz it could be caused by other problem( bending moment, self-weight...etc)...so I try to disable the UForce, but the problem is the same.

Is the result I got make sense? Or does anyone has better idea to create a inflate-sphere by acting the radially loads?

By the way, the cushion can looks total different when it create by 'Pressure' instead of 'MeshPressure'.

Attachments:

Pressure.3dm, 205 KB
Pressure.gh, 28 KB

Replies to This Discussion

Permalink Reply by Alejandro REBOREDO on November 5, 2014 at 6:46am

As I can see... your surface is not exactly half an sphere..... maybe a spheric dome. but not half a sphere.

I assume the scenario of that surface being afected only (or mainly) by internal pressure

In my opinion that is the cause deformation isn´t spheric.. forces and reactions in the restricted edge should be vertical or at least allmost vertical.

Even if it was half an sphere deformation wouldn't be regular as you need a whole sphere to achieve that.

Permalink Reply by Jon on November 12, 2014 at 9:42am

Hi Alejandro,

thanks a lot...I think it make sense coz the forces and reaction in the edge are just different than other...

in contrast, a completely perfect sphere wouldn't cause the deformation if the air pressure as radially acting loads...theoretically...

Probably Daniel have something additional to explain?

Permalink Reply by Daniel Piker on November 15, 2014 at 3:18am

Hi Frank,

-Both the Pressure and MeshPressure components work exclusively on triangle meshes. If you give it quads, you may get some strange results. So always triangulate first (and I'd also recommend to split each quad into 4 triangles using Weaverbird's stellate, to avoid introducing unwanted asymmetry)

-Pressure applies a given force per unit area, and this value only changes when you change the input

-MeshPressure is volume dependent, so as the volume increases, the pressure will decrease.

-It is true that pressure will make things tend towards spherical, but the shape you get from inflating a mesh is also affected by the mesh geometry and stiffness, as this is what is resisting the pressure. In your second image down, it is expanding more at the sides because the mesh is less dense there, so less resistance.

-If you did want the stretching resistance of your membrane to not depend on mesh density, you could use the soap film element (and in this case you would also need GStrings to keep the mesh from degenerating, as soap film elements alone have no shear resistance).

I hope that clears some things up,

Daniel

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