topic Re: Simulation with superelastic Nitinol in Inventor Forum

Simulation with superelastic Nitinol

Anonymous — Wed, 13 Dec 2017 15:46:16 GMT

Hello everybody,

have any one of you experience with superelastic Nitinol?

I have to simulate a load of a model with Nitinol, so I generate Nitinol in the material box. Now the issue is that I can't say this material is "superelastic" and it has different stress plateaus.

As result I get high values (and high differenc between the lowest and highest load) and the message that I have to check the load and the subjection.

Do you have an idea how I can slove my problem and work with a superelastic nitinol?

Insert Material dataResult of the simulation

Best regards

Re: Simulation with superelastic Nitinol

john.vellek — Wed, 13 Dec 2017 15:59:19 GMT

HI @Anonymous,

Did you want to post this in the Simulation forum rather than the AutoCAD forum? If so, I am happy to move this thread. Sadly, I have no experience with Nickel Titanium but I hope the Community can offer some suggestions.

Re: Simulation with superelastic Nitinol

Anonymous — Thu, 14 Dec 2017 11:49:07 GMT

oh, I'm sorry

Yes, please 🙂

Re: Simulation with superelastic Nitinol

JDMather — Thu, 14 Dec 2017 14:39:35 GMT

@Anonymous

Based on your other posts to the forum I would assume that you are using Autodesk Inventor.

Is that correct?

If so, the Inventor forum is over here

https://forums.autodesk.com/t5/inventor-forum/bd-p/78

Inventor FEA is limited to:

The linear static portion of the stress/strain curve. (Your description sounds like non-linear analysis).

Isotropic materials (material properties the same in all directions).

Relatively small displacements. (your displacement might violate this limitation as well)

Do you have access to NASTRAN In-CAD through your license?

Are you a student?

Re: Simulation with superelastic Nitinol

Anonymous — Thu, 14 Dec 2017 16:05:03 GMT

Hello,

Yes that's right. I am a student and use inventor.
I recently downloaded Nastran in CAD, but I don't have an overview of the program yet.

Yes my system is not linear as long as it is not plastically deformed.

Re: Simulation with superelastic Nitinol

Anonymous — Thu, 14 Dec 2017 19:12:15 GMT

What you're asking for is the stuff of numerous doctoral theses. The plasticity part is just the tip of the iceberg. It's also 'super' temperature dependent, and even path dependent (meaning you have to keep track of the material's history). There is a lot of literature on this (ASME, SPIE) that you can draw from. You should do your research before you dive into it. It's a hard problem by any measure.

Inventor's simulation cannot solve this. It can only do linear problems with small displacements, as JD said. Nitinol is the poster-child of nonlinear, large displacement, hysteretic, ill-behaved materials. If I recall correctly, either ABAQUS or ANSYS has Nitinol elements available, but it's not something you'll just 'do' and make it work and get a good answer. You'll really need to understand what you're modeling and how it's implemented in the code or you're very likely to get garbage results.