topic Re: Simulation incoherence in Fusion Support Forum

Simulation incoherence

Anonymous — Thu, 17 Jan 2019 09:28:52 GMT

Hi everyone !
I'm posting today because i can't any solution to my problem by myself...

I'm currently working on a student group project, and i'm modelling an orthesis (dunno if that's the word) but it's basically and orthesis that is around the leg of some that does have muscle problems.

The fact/problem is when i'm applying a force on the top part of this piece, my intuition is that the heel should move (at least a little bit).
It seems stuck into the ground even if it's not constrained in any direction.

I've tried with a higher force but the heel doesn't want to move along with the top part..

I've uploaded a screenshot so that you can see what the problem is. Thank you guys for your help 🙂
Here is the link to the model : https://a360.co/2TX4yHW

Re: Simulation incoherence

mcmillr — Thu, 17 Jan 2019 18:30:45 GMT

Antoine, the result is correct. The sides if the heel are acting as 'ribs' and stiffening the entire heel area. If you display stress you will see some color on the heel and sides. Just to make sure I ran this as a nonlinear analysis and got an identical result. Nonlinear is more accurate when there is a 'large displacement', which in your case could be a factor. I also tried placing a local mesh refinement on the sides of the upright section to ensure there were multiple elements through the thickness, but once again the result was the same.

Re: Simulation incoherence

Anonymous — Fri, 18 Jan 2019 08:41:17 GMT

Hmmm...

Note so sure about that because even when the force applied to the structure (on the top part) is equal to let's say : 200N, the heel doesn't move.

And the fact is that the material is quite rigid and all the forces should be transmitted before the elastic deformation and in this way, the heel sould move just before the moment when the top part is elasticly deforming.

Maybe split the bodies would change something ? Do you have an idea on how to do it (split between the "blade" and the heel)

Thanks !

Antoine S

Re: Simulation incoherence

TheCADWhisperer — Fri, 18 Jan 2019 15:54:31 GMT

Is Carbon Fiber an isotropic material?

Re: Simulation incoherence

mcmillr — Fri, 18 Jan 2019 22:42:50 GMT

Splitting the bodies should not make any difference, and you usually get better results when you have a continuous mesh as opposed to defining contact between non-conforming mesh regions.

I am not a material expert, but the definition of carbon fiber with a resin is 'extremely strong but flexible'.

Your thin upright section is flexing much more easily than the 'cup' shaped region of the heel. If the material is more flexible than it should be, you should check your custom material definition. If the material is truly not isotropic, then Fusion cannot give the precise answer because it only supports isotropic materials at the moment.

By the way, the heel DOES in fact move, just very slightly in relation to the area where the load is applied. Under Inspect you will find 'probes' which you can see that the heel is displacing about 0.1 mm.

Re: Simulation incoherence

Anonymous — Sat, 19 Jan 2019 17:01:03 GMT

No, the fiber inside the resin matrix are oriented : it's not an isotropic material

Re: Simulation incoherence

Anonymous — Sat, 19 Jan 2019 17:18:34 GMT

The problem was in fact in the constraints, the material is quite stiff and the object was contrained also in the left and right part of the feet, and so the heel couldn't move.

With some tweaks in the constraints, the heel can move freely