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How come the "pushingforce" drops to zero at the peak of the snap?

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How come the "pushingforce" drops to zero at the peak of the snap?

Hello,

I don't seem to understand why the results are as shown in the attached picture. I'm performing a contact analysis in Creo 3.0 Simulate; the force increases as it should but the when the structure has moved down about 3mm the force drops to zero and then increases again.

How can I fix this problem?

Would it help to do a finer mesh in the area of contact?

Thanks.

- Ahmad

8 REPLIES 8

Re: How come the "pushingforce" drops to zero at the peak of the snap?

I tried changing element size at contact areas and i guess i got a better result, but it still goes to zero.efter element size.PNG

Re: How come the "pushingforce" drops to zero at the peak of the snap?

Are you using finite friction in your contacts?

Re: How come the "pushingforce" drops to zero at the peak of the snap?

yes, with a static coef. of friction at 0.6

Re: How come the "pushingforce" drops to zero at the peak of the snap?

Re: How come the "pushingforce" drops to zero at the peak of the snap?

so is what im supposed to understand that creo 3.0 simulate does a poor job at contact analyses with finite friction?

Re: How come the "pushingforce" drops to zero at the peak of the snap?

Hello Paul,

Thanks for the link.

Their documents are always very interesting.

I always look at if I just find new ones.

I already own several, but not the latter.

Kind regards.

Denis

Re: How come the "pushingforce" drops to zero at the peak of the snap?

Can you provide more information about the nature of the problem you're looking at? It's hard to tell from the image(s) you've posted, but what could be happening is that you're experiencing a 'snap-through' effect. These are dynamic events, where the path is driven by the inertial forces, which is something that you're not going to capture accurately in a static (or quasi-static) analysis.

You can try to take finer steps around where it goes to zero, but this could potentially cause convergence issues. Mechanica does have a 'snap-through' option to try resolve some of the convergence issues, but the last time I checked (which was maybe a year ago), this option was essentially broken.

Re: How come the "pushingforce" drops to zero at the peak of the snap?

think of it as a cylinder where you push down a snap. This means that the snap doesn't actually "snap in" it simply "slides" into the cylinder. Could it really be the snap through effect for this case?

I'll definetly try to run the analysis with finer steps.

thanks.

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