The model does not contain sufficient restrictions

[DenisJaunin]

Hello

I have a problem with a simple Assembly of 2 parts with contact.

I have four branches in in AU4G on the what is exerts a force.

The branches are retained by a steel pin which is constrained.

But every time I get the following message:

The model does not contain sufficient restrictions for this analysis.

Check the restrictions, properties and binding elements.

I can't understand my mistake?

Kind regards.

Denis

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[danderson]

Hi Denis,

Try adding 3 ground springs with spring with properties of almost 0 like 1 or .01 to the thru hole in the part that has the 4 fingers that you are apply the load to.

Right now it's not able to define the initial location/state of the part on the left (is it touching the shaft or is it centered around the shaft).

Once the ground springs are added it should solve with no issues.

Hope this helps,
Don Anderson 

[DenisJaunin]

Hello Don Anderson,

Thanks for your reply.

I placed the 3 springs of soil at the indicated places but I still got the same error.

Kind regards.

Denis

[DenisJaunin]

Hello

I enter the PIN in a fixture irritated.

PIN na more constraint fixing.

And I still got the same error.

Kind regards.

Denis

[danderson]

Denis,

Per your last picture you would need 3 ground springs on the part that you are applying the load to and 3 ground springs on the pin connecting the 2 rectangular parts.

Also you would need clearance in the bores for the pin in order for the contacts to work properly unless the pin is a press fit. If the pin is a press fit then you will need the pin to be in a non assembled state and apply a fixed distance displacement constraint to assembly the pin to make the contacts work properly.

Hope this helps,

Don

[DenisJaunin]

Hello Don,

Thanks for these remarks.

I am running 3.0 M080 Creo.

I replaced tensile stress with displacement by force.

I still have the same error.

I really can't understand why it does not work.

I make several assemblies with contacts without problem.

I've never used this principle of the springs with the ground.

Kind regards.

Denis

[danderson]

Denis,

The example I have attached is based on your original image you posted of your problem.

I made a lot of assumptions like I'm assuming you have a clearance hole between the legs of the rectangular part and the pin and that you are only constraining it at the ends of the pin, material?

I added surface regions for each contact and for each displacement constraint.

I have added 3 springs to stabilize the parts so the analysis can begin from a know starting point.

I have added contact to each of the fingers

I constrained the ends of the pin

and applied the material to each part.

If the pin has a press fit you will need to use a deferent model setup than what I have provided,

See if the attached files help,

Don Anderson

[DenisJaunin]

Hello Don,

Thanks, this is awesome, it is exactly that.

Compared to you, I had forced the entire surface of the PIN but not only the ends.

The side that has the two springs deforms more than the other.

For contacts, you set each link in advance to the PIN and selected one by one.

You did use the function detect the contacts automatically.

On the PRT0002, the first "leg" is a surface area and the other three a volume region, it is done on purpose?

I did a test by removing your Springs, I received the error message.

Now how can we learn how to put these springs in the right place?

I feel sorry for all these questions, but I just learned a new way to work with Simulate.

Kind regards.

Denis

[danderson]

"You did use the function detect the contacts automatically."

No, I manually applied each contact constraint.

"On the PRT0002, the first "leg" is a surface area and the other three a volume region, it is done on purpose?"

All of them are surface regions. I made a mistake on the first on in PRT0002 and sketched it a little short. it stops in the middle of the pin and should have run completely across the pin.

"Now how can we learn how to put these springs in the right place?"

The springs are used to lock down parts that have degrees of freedom. When using contacts you are allowing the interfacing parts to move freely. These degrees of freedom need to be locked into an initial state or location to give the calculations a point to start from.

If you have a loose pin in a door hinge  it would fall out. One ground spring to hold it in the general area of the hinge, a second ground spring to keep the pin from spinning about its axis, and a third ground spring to prevent it from tilting in the bore of the door hinge.

Hope this helps,

Don Anderson

[DenisJaunin]

Hello Don,

Thanks for this valuable information.

I'll resume my template to apply this method.

Kind regards.

Denis.