Karamba Internal Pressure strengh

hi i’m trying to add internal pressure force as a load, but don’t know how to add it using the karamba plugin, I am trying to find out the required specific strength for the shell, with a very high internal pressure.

fea4.gh (37.0 KB)

Hi @lucianatenorio,
you could use a MeshLoad-component (see here):
fea4_cp.gh (42.7 KB).

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thank you! but the force is in z, what if I need the pressure force to be distributed proportionally along all the ellipsoid surfaces to mimic a super pressure balloon?

The load is oriented locally and thus acts like pressure perpendicular to the mesh faces.
– Clemens

I continue with the simulation but somehow I’m having very different results from a lobed cylinder shape and a normal cylinder, both with spherical caps, even though I’m using the same surface load vector (100 kN/m2) the results are very different, the stress in the lobed structure should be reduce because of the local small radius, but that isn’t happening, there is too much deformation happening. and some parts are working in compression, when the whole should be working in tension.

pumpkin cilinder lobed.gh (54.9 KB)
cilinder pumpkin.3dm (2.4 MB)

i also had some trouble adding a weavebird geometry as I can attach it as a brep and reduce the mesh resolutions, this file is turning pretty heavy to manipulate, and the load isn’t being recognized

pumpkin cilinder lobed_weavebird.gh (50.5 KB)

Hi, your mesh is way too dense, so you need to reduce the density, but also you do not need to input the thickened mesh but just the singular axis mesh.

I reduce the mesh a bit, but I change the units of the rhino file in cm as the stress result is on KN/cm2 (does that has something to do?) Karamba has some units in kn/m2(loads) and others in kn/cm2 (stress) can I change that?

I don’t want to reduce too much because it will change the spherical shape and that’s what I want to test the lobed surface as the shell. but now I notice the pressure in the bottom part is coming from outside, in the whole model is supposed to come from the inside.

I also change the material to isotrop, im using a polyester film using it for its high tensile strength

pumpkin cilinder lobed_material.gh (62.4 KB)

hi, you need to align the mesh faces so that all the normals are in the same direction:

Karamba inteprets all geometry units to be in m (no matter what your rhino file is). The units for the loads and stresses cannot be changed. These are standard units that are used for these properties.
pumpkin cilinder lobed_materia-mt.gh (67.5 KB)

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