Karamba - user problems

please post here in case of karamba problems !

Replies to This Discussion

Permalink Reply by riccardo foschi on February 11, 2020 at 12:04pm

yes that what I meant, so this means that in this case the shell calculation is not suitable, do you think that substituting the shell type with a beams and pillars structure could solve the problem? I would put the beams on the sharp edges of the original surface. and maybe to have comparable results I could equalize the volumes of materials shrinking the sections of the beams in one of the two systems

Or does it have the same problem of the shell type?

Permalink Reply by Karamba3D on February 12, 2020 at 12:59pm

Dear Riccardo,

what type of results do you want to get out of the calculation?

Is the original geometry a filled or a hollow cylinder?

Permalink Reply by riccardo foschi on February 13, 2020 at 1:05am

it's a hollow cilinder, and I would like to compare the vertical global displacement of the structure in two similar but not equal structures. I'm not sure if the karamba calculation of beams consider axial deformations correctly.

Permalink Reply by Karamba3D on February 13, 2020 at 12:08pm

Do you have an estimation for the results from e.g. a hand-calculation?
Correspond these results with what you get from the Karamba3D analysis with shell or beam elements?

Permalink Reply by riccardo foschi on February 14, 2020 at 4:08am

Let me explain a little better what I'm trying to get. Until now I tried to be synthetic but I understand that it's not clear enough.

I'm trying to compare two structures that should be fabricated by folding a very thin metal plate.

the two structures have a different crease pattern but the same volume of material used (and the metal plate has the same area when developed in the plane).

I was able to achieve a credible simulation with fusion 360 that uses solid fea (not beam nor shell). When I say credible result I refer only to the deformation (I don't care about stresses even if one is the consequence of the other).

I know that is credible because I get more vertical displacement in the structure that have the surfaces more angled in relation to the vertical axes.

In Karamba no matter what I do I always get equal global displacement in both the structures even if they are a little different. I'm aware that the bems and shell are not correct to approximate the behaviour of a continuous folded surface, that is why I used fusion in the first place, but I was wondering if there is a way to approximate it anyway with beams, maybe placing them in correspondence of the creases and leave the faces empty, in this case I probably should change the section of the beams in relation to the area of the adjacent faces? or something like that?

However, I want to implement in grasshopper the calculation to use later a genetic algorithm to ask grasshopper to find the variation of the pattern which deforms less with both vertical and horizontal stresses.
The problem is that in Karamba there is no solid simulation, and I'm starting thinking that I can not approximate the behaviour of such a structure with beams or shell elements at all.
What do you think?

Permalink Reply by Karamba3D on February 17, 2020 at 12:21pm

For the type of structure you describe which consists of thin, folded metal plates a shell analysis should be fine.

Did you try out different mesh densities to check whether the displacements you get are correct? In case of shells a mesh which is too course underestimates the displacements.

Start your tests with simple geometries - e.g. straight wall vs. wall with one horizontal fold. Then increase the complexity.

Permalink Reply by riccardo foschi on February 17, 2020 at 1:19pm

I already tried increasing the density of the mesh, but I always get almost equal deformations in both structures, but the idea of testing it on a straight wall is a good idea, i didn't do it yet. I'll try it and I let you know.

Permalink Reply by Shukey Lin on February 21, 2020 at 8:21am

Hi, I am new to Karamba3D and I would very much appreciate some help with the software.

I have a truss that is illustrated in the figure below. The truss is composed of two individual components (one of the components is outlined in red for illustration). The two components are connected through bolts at the black circled areas. How can I go about modelling the bolt within the program?
I want to define the load on the truss as an area load. I have made a mesh as illustrated in the figure, and attempted to apply a uniformly distributed loading over the mesh. However, I am not sure if it’s actually working, since the element at the mid of the top chord doesn’t seem to be registering any load. Please let me know if I am on the right track and how I can proceed, or if I should use another method to apply area loading.

Thank you for your help!

Permalink Reply by Karamba3D on February 27, 2020 at 12:55pm

Hi Shukey, you can model the bolts with hinges (see here and here). They can be equipped with rotational and translational stiffnesses if necessary.

Regarding the MehLoad: Make sure that the mesh on which you apply the load is fine enough. Also change the default values for the graphic segmentation of the beams in the ModelView-component in the submenu "RenderSettings" under "Length/Segment".

Best,

Clemens

Permalink Reply by Maria Tsepaeva on May 5, 2020 at 9:14am

Hello,

I have a little problem installing the license. I use Karamba for Rhino 5 and up to this moment I had one-month trial license, it worked correctly and I didn’t have any question with it. But now for continuing working with Karamba for my internship I’m trying to set Research and teaching license. I tried to install it several times with tutorial, by Karamba license-component and manually, but unfortunately, it doesn’t work. Actually the date of expiration has been changed but license type is still "trial" karamba.png. I reinstalled Karamba to verify if it's a full version, but still nothing. So, I can’t find where the problem is…. If someone know how to solve it, I would appreciate any help.

Thank you.

Best regards,

Maria

Permalink Reply by Matthew Tam on May 5, 2020 at 10:18am

It seems there is an error with the license with older versions of Karamba - please update to the newer version - https://www.karamba3d.com/nightly-builds/karamba_LATEST_VERSION/

Permalink Reply by Maria Tsepaeva on May 5, 2020 at 12:24pm

Thank you very much for your quick reply