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Force to close a

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Alexandrite

Force to close a

Goodmorning,

I have a following question: Is it possibile investigate with Creo Simulate the value of the force in order to "close"

the purple solid against the Yellow solid.I need a non-linear analisys, right?

Thank you for your help

 

 

Tags (3)
20 REPLIES 20
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Re: Force to close a

Yes you want non-linear.  Large Deformation and possibly Elasto-plastic material

Here is the difference in small displacement and Large displacement (small on left)

 

Bendy1.JPG

 

Here is how you do the 1.4mm deflection

Bency_enforced_displacement.JPG

 

Here is how you prevent infinite stress at the edge constraint... with a small region made rigid.

Bendy_rigid_region.JPG

 

 

Here is the measure used to obtain the force.

Bendy_reaction_Force.JPG

 

 

Here are the Analysis definitions.  If using elasto-plastic material then Plasticity will have a check mark.

Bendy_Analysis_Def1.JPG

Bendy_Analysis_Def2.JPG

 

 

Plotting the measure vs. time

 

Bendy_graph_Force.JPG

 

 

Final results.  If stress is above yield then you should use ELASTO-PLASTIC material.  Nonlinear material + non-linear geometry.  Otherwise force is generally predicted too high.  

 

Bendy_result.JPG

 

Confirmation?  Run this model with found force (48N in this case) in X direction as a load in place of the enforced displacement.  Confirm max displacement about 1.4mm in X direction.

 

 

BONUS - I used a Mapped Mesh (not totally necessary but results are so smooooth!)

Bendy_Bonus_Mapped_Mesh.JPGBendy_Bonus_Mapped_Mesh2.JPG

 

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Re: Force to close a

Thank you for a good response

but I'm not able to open the file.....

 

 

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Re: Force to close a

That is why I had all the details... because not everyone is using the same version.

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Re: Force to close a

But for Use "ELASTOPLASTIC" material is correct this?

 

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Re: Force to close a

Yes.

 

Use creo help to understand elastoplastic in Creo.

Link to help

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Re: Force to close a

Simulate said me that costraint and rigid link on surface region to prevent infinity stress is incompatible...

 

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Re: Force to close a

This is OK.  It is a warning, not an error.  Only use caution when this message appears because you may be asking the model to do two different things at same time.

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Re: Force to close a

What You do in your model? You used the same way or an other?

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Re: Force to close a

Same way.

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Re: Force to close a

Hi!

I used an elastoplastic material, but obtain this warning message with high stress

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Re: Force to close a

Please show more views of your model.  Is there a location with a sharp inside corner like this?

 

All inside corners near areas of interest should have at least a small radius.  For the plastic parts I work with 0.15mm radius is used.  Compared to H-elements, P-elements are less forgiving.  In H-elements the stress is averaged over the element size which hides the singularity until using smaller and smaller elements.  For P-elements the order of the element captures the high stress with larger elements.  You can artificially limit the order of the elements near singularities but I prefer a tiny, but realistic radius.

 

What strain is it reporting vs. what you expect?  Are you using a force or an enforced displacement.  With a force this same message often comes when the design cannot reach the load applied, sometimes even failing to finish the loadsteps.  I also suggest to plot a measure of plastic strain or stress vs loadstep.  You can stop the analysis and view intermediate results at each loadstep.

 

Finally element quality/number will affect the ability to model large strains.  A mapped mesh with quads and more layers through the thickness will help capture larger strains without too much element distortion.  A tetra mesh with large elements could contribute to the issue.

stress riserstress riser

 

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Re: Force to close a

Hi, 

I try to improve my model, but I obtain again high stresses;

I added a small radius where the displacement occurs and mapped mesh

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Re: Force to close a

modulus.JPG

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Re: Force to close a

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Re: Force to close a

no

tan_mod.JPG

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Re: Force to close a

In this way the values  of stress down, but there is again the warning

"** Warning:
The stress is much higher than the yield strength of one of the
elasto-plastic materials in your analysis. Please review
your material properties and/or units."

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Re: Force to close a

wrong.JPG

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Re: Force to close a

Where did you find this value (1000)?

The data sheet I mean.

Thanks

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Re: Force to close a

it's approximately, circa

tan_modulus.JPG

Re: Force to close a

pressure_opt.jpg

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