Kangaroo - How to avoid rotation of lines with bend forces

Hi guys,

I'm trying to simulate in Kangaroo the behavior of a Textile Hybrid structure that is composed by a pre-stretched fabric and a zig-zag shaped 3D printed plastic. The idea is to simulate the transformation of the structure when the fabric is released from its pre-stretched state.

I have the issue that the bend component of Kangaroo doesn't avoid the rotation of the lines while keeping the angle between vectors. This rotation introduces undesired forces. Does someone have an idea on how to avoid this rotation? I've already tried with the shear, vortex and the hinge component without success. But I'm not so experienced.

I tricked a little bit with some springs in between the top points of the zig zag (that I should add diagonals to improve), but this fix is introducing undesired forces to the system that distort the solution.

I'm attaching some pics of the screen, some physical samples for references and my definition.

Any help will be very valuable for my research.

Best,

Jorge.

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Permalink Reply by martyn hogg on August 14, 2016 at 1:02pm

I'm no expert either but I thought I'd chip in...

I would start by trying to simulate the fabric only because you should know the shape it should return to without the 3d printed structure. i.e. can you make the curved mesh of the fabric return to a flat rectangle by using Kangaroo?

If that works, then try and add the 3d printed material into the simulation. Perhaps by using the angle component which tries to maintain an angle between the lines representing the 3d printed structure.

Permalink Reply by Jorge Christie on August 15, 2016 at 1:38am

Hi Martin, thanks for taking some time with my problem.

Indeed, the fabric is already working as a proper stretched fabric and it's returning to the pre stretching state with the coefficient I measured from the actual fabric.

The point is that the deformation of the fabric (surface curvature) is produced by the force dialogue between both, the stretched fabric and the bending strength of the 3D printed plastic. I am using the BEND component to simulate the plastic. The only problem I have is that this component only restricts the angle between two vector, but doesn't fix the rotation of one around the other while is keeping the angle. This is the key point, because is causing the triangles of the same row to loose the alignment, therefore, introducing random forces to the system and distorting it.

Thanks!

Permalink Reply by martyn hogg on August 15, 2016 at 10:09am

Kangaroo2 has a goal object called OnPlane which tries to keep points on a plane!

Could you use this to keep the 3 points that make up the 3dprinted struts planar to stop the rotation?

Permalink Reply by Jorge Christie on August 15, 2016 at 10:50am

Hi Martin!

That's a good idea. I haven't used Kangaroo 2, but I guess is not so different from the 1. I was actually trying the same with the SHEAR component (which I guess is equivalent to the one you suggest), but somehow it was spitting me an error.

I will see what happens.

Thanks a lot!

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