metal bellow

[Ragsta]

hello to all

It's just that I've been using ansys and given the infinity of errors that you can make I address to you.

I have to simulate a metal bellows made of two lamina of 0.25mm thick subject to a compression of about 170n.. .simulation that should be really simple but...

from experimental tests the bellows should compress 3mm but simulating with ansys the result is 2.1mm.

I initially thought it was due to the mesh but also infixing the result does not change, then I tried to verify the type of element used but also in this case I got the same result.

for a further verification I checked that the thickness of the blades was correct and it was as specific (0.25mm) while on the simulation only going down to 0.22mm I have a shift as from experimental testing.

In your opinion, where I may have made a mistake, the bellows on ansys is too rigid.

thanks in advance

 

[stefano.garbin]

two small ideas:
1-consider well the way your model is bound. often and willingly it tends to over-win, thus obtaining excessive rigidity.
2-to the eye you are not in regimen of small shifts, have you activated non-linearity? with classic ansys, solution->analysis type->sol'n controls and analysis options select "large displacement static". or on the command line write "nlgem,on"

 

[Ragsta]

As for the constraints I only stuck the scroll in y on the lower part of the bellows.

You're right I'm not on small shifts so before launching the simulation I had already activated the "large displacement"

Anyway, thank you.

 

[stefano.garbin]

mmm, that sounds interesting. . .
How's that piece? Asymmetrical analsis?
how were these 170n measured? is it not that by chance a part of the load cell caught friction forces etc.?
You know, it's not said that your data is always right. .

 

[Ragsta]

analysis is pure asymmetrical.

the load I measured it directly on about 6 bellows and repeated 2 times attic.
I am quite confident that the test bed load is correct, as in line with the specification given to us by the bellows supplier.

 

[Ragsta]

I forgot to specify the material:
inconsulated 625
ex=2.08e11
nu=0.28