MN-bending-analysis

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Comment by David heaton on November 23, 2015 at 3:11am: Is it possible to share the script you used in creating the video from below with the plywood stips? Thanks!

P.S. Your blog has been really helpful in understanding how to work with bending :)

Comment by Rasmus Holst on October 22, 2012 at 2:07am: Okay... I know that as long as we look at things as being linear elastic, it will be the same, but strength/resistance and therefore stresses and connection forces will be different for different materials and cross sections.

The fixed joint are only an early test, I think that I will connect them via some sort of spring or sliding joint.

I still have to figure out, how to control my inputs for Kangaroo correctly though, so that I can trust the output as much as possible in the end.

Thanks.

Comment by Mårten Nettelbladt on October 21, 2012 at 1:24pm: There is no real difference in bending geometry between for example plywood or a steel saw blade. Cardboard will bend differently, but that's because it's not elastic enough (some plastic deformation instead of elastic).

My input values don't really have units, but they really are is Curvature = change of direction per distance along curve).

Thanks for posting your gridshell tests. One question: Why do you fix (glue) the joints? Do you want to prevent them from becoming double curved?

Comment by Rasmus Holst on October 19, 2012 at 6:41am: Hej Mårten. Thanks.

Okay then I understood correctly.

When you have used Kangaroo, have you managed to translate the numeric input values to real material properties? For the plywood you have bend for example? Or how do you think about this? I am doing my master thesis in Architectural Engineering about Parametric Design. So for the time being I want to simulate the effect of twisting and bending of regular wood elements. So I need to simulate one strip correctly so that I can simulate the formation of a gridshell...

I have some small test on youtube:

http://youtu.be/cC4zV9YzUxk

http://youtu.be/-Yp5ICbbqtE

http://youtu.be/-s-RHU2330o

Nothing you haven't seen before though.

Your values of Bending and twisting, what units are these in? And do you calculated from the curvature?

Sorry for all the questions :).

Rasmus

Comment by Mårten Nettelbladt on October 18, 2012 at 2:12pm: Hej Rasmus! Yes, that is exactly what I meant. Please show me more of what you are working with! /Mårten

Comment by Rasmus Holst on October 18, 2012 at 5:29am: Hi Mårten.

First of all, great work. I am working on similar things as you, working in Kangaroo at the moment though. I have seen different places where you describe the twisting (/torsion?) as direction of bending or like here curvature direction. Correct me, if I am wrong. I find this way of looking at it really interesting, but I am not sure I understand completely what you mean by, direction of bending, is it the angle of the bending-line in the plane? Compared to the line perpendicular to the edge? Or how should I interpret it?

Hope you understand what I mean? :)

Cheers Rasmus

Comment by Mårten Nettelbladt on March 14, 2011 at 2:49pm: Hi Valeria, thanks for getting in touch. I'm glad you're using Tapeworm!

Using a fixed endpoint is not possible with tapeworm I'm afraid, because of the way it works.

You would probably need something like Kangaroo for this. In this video Daniel shows how to simulate bending of a rod with fixed endpoints:

http://www.grasshopper3d.com/video/kangaroo-bending-validation

I made a similar test:

http://www.grasshopper3d.com/video/kangaroo-bending-reactivision

Doing the same thing in 3d with a developable ribbon (like tapeworm) is a little more tricky. I've made some attempts (with the help of Daniel Piker), but yet I have no usable results:

http://www.grasshopper3d.com/group/kangaroo/forum/topics/double-loo...

http://www.grasshopper3d.com/group/kangaroo/forum/topics/bending-re...

Please post some images from your tests, it would be fun to see!

Comment by Valeria Sanchez Roji on March 14, 2011 at 1:27pm: Hello!!

I'm working with a team and we love what you did with the tapeworm component! Actually it is part of our deffinition but we are having a little problem. We need to have an endpoint so that we can modify the curvature in the tapeworm but still have the same specific point where it must end...

We know you can modify the lenght and the start point, but is there a chance that you can help us with the endpoint?

Thank you!!

Comment by hamia Aghaiemeybodi on February 4, 2011 at 2:13am: good point . . . thanks a lot . . .

Comment by Mårten Nettelbladt on February 4, 2011 at 1:54am: The key (for me) to get this right was to model a flat approximation of the surface. This way it's easy to make sure it stays single-curved and "straight". In the image below, angels A+B should = 180°, the same for C+D. E is the curvature. Afterwards create two interpolated curves from the vertices and loft them. If the steps are small enough, the resulting smooth surface will be 100% developable (and straight when unrolled).