Help needed for NX nastran 2

[harshitbhatt]

I need help in doing simulation for finding deformation of a model but I am getting the following error:-

"SYSTEM FATAL MESSAGE 3000 (SITDELC)
ITERATIVE SOLUTION FAILED DUE TO FAILURE OF PRECONDITIONER TO FACTOR.
THIS ERROR CAN RESULT IF THE STRUCTURE IS NOT RESTRAINED SUFFICIENTLY TO PREVENT
RIGID BODY MOTION OR IF INTERNAL MECHANISMS EXIST."

Please help me out.

I have attached my file for the reference.

 

[harshitbhatt]

@Tuw thanx for the reply sir.The moving plate is actually a ring which will rotate and this is how its moving, not horizontally.I have taken just a part of the whole ring. All this parts are 360 deg.I have taken just 1 deg.

I have fixed the CG of moving plate as I need to find deformation of whole plate.The cylinder should deform between the two plates.The upper surface of cylinder has 20 bar pressure and lower surface has 1 bar pressure.So due to this it should go towards the left side of two plates.The cylinder is a O-ring. This is actually a DRY GAS SEAL.

 

[Tuw]

Hi Harshitbhatt,

Please find attached file for your reference.

For your information, your loading condition is pressure, which is quite challenging because pressure or force load would induce inertia effect. In order to ignore the inertia effect, I change the pressure loading to enforced displacement, which is better in convergence. Again, this goes back to your analysis objective, what is your analysis purpose? will this act against your purpose..

All in all, you have a lot to study...

 

[harshitbhatt]

@Tuw thank you for the reply sir.Sir I saw the file you attached.Thank you for your valuable time.Actually I need to find out the deformation of O ring[Cylinder] and while it deforms what deformation we get in another two. I have attached my simulation.If you can see to it.

When you will see the result,you will see that when O ring is getting in between the two,the edge of upper plate gets deform.I was looking for that but still the O ring should squeeze in between the two[change its shape for like circle to oval or something].This is not happening.

Thanx for the reply sir.......

 

[Tuw]

Hi Harshitbhatt,

There are many reason/factor to view deformation. Some point you should take note.

1. Your analysis is considered as high complexity or nonlinearities. Therefore, when you build your simulation model, please do it by adding complexity gradually and slowly. The way you do contact definition is not recommended, because you are trying to dump everything/ every surface into 1 definition. Remember, split the definition into several simpler definition, 1 surface versus another 1 surface. This is the way of professionalism.

2. When you are working with Sol601106, that means your are taking into consideration of boundary nonlinearity or time. If you want to see deformation, define a time. We don't expect the deformation can be achieved within 1 single loop of iteration, do we?

3. Furthermore, if you insist of using pressure or force loading condition, I think the more suitable solution would be Sol601129, which take into consideration of inertia effect. Please take note that for this solution, you will need to have very fine time step (i.e. 0.0001sec per step or smaller). You might have challenge to get the right time step to achieve convergence.

4. Did you define a proper o -ring material using the correct material model, for example hyperelastic material model? Did you have the material data sufficient, for example the stress strain curve?

Please don't expect to get a quick solution here. A successful and meaningful simulation is tonne of hardwork and patience.

Regards,
Tuw

 

[harshitbhatt]

@Tuw Thanx for this reply sir.Helped lot.I will do it as you said.....

Thank you for your reply.And what should I do in my simulation to get better result.First of all is it correct?

The file I uploaded.

 

[Tuw]

Hi Harshitbhatt,

Good question. This address lack of confidence. Always beginning your simulation with a simple one. For example, you can just do a simple compression simulation between 2 components, not necessary to follow the actual geometry. It can be a cuboid and another sphere. Check the deformation whether as expected. If not, there is no meaning to add more complexity, but to focus on this study. Then, once you achieved this, add more complexity, 1 by 1. Do 1 study at a time. This is the way to gain confidence. The truth is your work is not professional.

Some study you may consider:
1. Use enforced displacement first, before proceed to use pressure loading because it is more difficult to converge.

2. Use user-defined constraint. Learn about DOF (degree of freedom).

3. Use Sol101 first before using more complex solution. Understand limits of Sol101 (linear static).

4. Learn about meshing, geometry idealization and mesh quality.

5. Learn about to constraint your model in cylindrical coordinate system .

6. Get the material specification of the o ring. Study hyperelastic material model.

7. Learn time step setting up.

8. Learn strategy parameters for Advanced solution Sol601106 and Sol601129.

Look up NX Documentation for explanation.

 

[harshitbhatt]

@Tuw thank you sir.Actually when I click on help in my NX 9 its not opening.Its showing some cannot connect to html file.My version is student version.

 

[Tuw]

@harshitbhatt, maybe you can read below link

http://www.eng-tips.com/viewthread.cfm?qid=354003

 

[harshitbhatt]

@Tuw Sir I did the same but not working .......

No I will try IIS.I didnt do that.

Maybe its student version so it may not work but I will try IIS.

Thank you sir.