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.

 

[Naffoussi]

Your model is not properly constrained, review your boundary conditions

Seif Eddine Naffoussi, Stress Engineer

http://www.Innovamech.com

33650 Martillac û France

 

[harshitbhatt]

yes sir I know but its not working out.The problem is with sphere I think so because if I don't include sphere it is working but adding sphere doesn't work.

When I modeled the geometry it was showing fully constrained and when doing simulation its giving the constraint error.

 

[Naffoussi]

May be you should create a spherical coordinate system and then fix some Degree of Freedom for some nodes just to avoid the rigid body motion.

Seif Eddine Naffoussi, Stress Engineer

http://www.Innovamech.com

33650 Martillac û France

 

[harshitbhatt]

kk sir I will try it now.

 

[BlasMolero]

Hello!,
Your model is not properly constrained as Seif explained, the sphere is free to "fly", if you run a modal/eigenvalue analysis using NX NASTRAN (SOL103) you will see the six rigid body motions in the sphere as six modes of value 0.0 HZ(the SIX DOF), the bofy is perfectly free to move in the space, and this is wrong in FEA: to get a valid solution you need to constrain your structure.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[harshitbhatt]

Sir I have given constraints but I cant figure out what mistake I am making.Actually I am new to NX.

The screen shot you posted, I think may be I am wrong, you must have given fixed constraints to both the plates but I need to give pressure on the plates and also the sphere and see the deformation [Both plates and sphere].

Can you please give me the files you have run if possible.And thank you for your comment.

 

[BlasMolero]

Hello!,
Well, is your model, yourself you can click in the FIXED constrain and you can see that the sphere is free, the model is not properly constrained, then the error ..

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[harshitbhatt]

Sir cant get cant get you...

"Well, is your model, yourself you can click in the FIXED constrain and you can see that the sphere is free, the model is not properly constrained, then the error .." srry

 

[harshitbhatt]

Sir I am getting error "Result is in wrong format".

Please help me

 

[harshitbhatt]

can we select a point or a node for giving constraints as when I select, whole surface gets selected.

A point or a node for giving constraint ?

 

[harshitbhatt]

@BlasMolero sir can you tell me what constraint you gave to the sphere?

 

[BlasMolero]

Hello!,
I didn´t gave any constraint to the sphere, I arrived to a solution because I ran a modal eingenvalue analysis (SOL103) where a free-free analysis could be performed: the analysis shows the rigid body motions that exist in a FE model and cause a singular matrix error in a Linear Static Analysis (SOL101). Please take a look here:

https://iberisa.wordpress.com/2011/...run-terminated-due-to-excessive-pivot-ratios/

In summary, if you want to arrive to a valid solution running a Linear Static Analysis (SOL101) you will have to constraint at least three (3) nodes of the sphere (not co-linear) in order to remove the rigid body motions in the sphere.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[harshitbhatt]

Thank you for the reply sir.I will try it to constrain the three nodes as you told and also try it with SOL103.Thank you

 

[harshitbhatt]

Sir its not working for me.Means its showing deformation but its not squeezing between the plates....

I need to do in SOL101 or 601.

 

[BlasMolero]

Hello!,
If you want to simulate "the ball squeezing between the plates" then you need to define surface-to-surface contact between the sphere faces & plate faces. Because you have a gap distance between the sphere faces and the plate faces, then the problem could not be solved as a linear contact problem using NX NASTRAN (SOL101) because you have large displacements, then the problem is fully nonlinear for the geometry: you will need to use Advanced NonLinear Solver (SOL601). A linear contact solution here is useless, simply colors ...
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[harshitbhatt]

@BlasMolero,

Yes sir I did the same.Surface to surface contact and SOL601.But its not squeezing between the plates.....

Cant understand what mistake I am making

 

[Tuw]

Hi Harshitbhatt,

About constraint, you did not apply any constraint at the sphere, even though you applied fixed constraint at the other 2 components. The solver will fail definitely in Sol101 because the ball is not fixed at all.

I don't understand what is your analysis objective is, but my suggestion is probably you can try to create a symmetry line to the ball, then apply symmetry constraint at the ball (provided you need to understand what and how to define a symmetry condition constraint using the user-defined constraint).

I noted that you would like to define constraint at "node" instead of "polygon surface". Yes it can be done, simply drop down from the No Selection Filter Drop Down List in the Selection Bar, and choose the Entity "Node" will do.

That's all about constraint. Next, even with constraint, the ball still cannot reach equilibrium without the support from its neighboring components. Therefore, you need to define contacts, like what Blas mentioned. To further enhance the contact between the sphere and its neighboring components, you can try to define a gravity load, which the direction of the gravity load helps to promote the contact definition (not the opposite direction with defy contact).

In my opinion, you can still try Sol101. If you need more help, please provide detail explanation on what your analysis objective is.

Regards,
Tuw

 

[harshitbhatt]

@Tuw thanx for the reply sir.

I did all what you said.Here is short description what I need.

My problem has two plates,one moving and one is fixed.There is a plastic cylinder between the two and presuure is acting on both the sides of cylinder and also on the two plates.

When I am running the simulation I am not getting the exact result which I should get[Deformation of the cylinder].The cylinder should squeeze in between two plates. My project detail [2D].

Here in 3D

I have uploaded my simulation file.If you can please see to it.

 

[Tuw]

Hello Harshitbhatt,


1. The Moving Plate is applied with a Fixed Constraint. So you want to move the plate, or you want to fix the plate??
2. The left side of the Moving Plate is 10bar, the right side is 20bar, so the Moving Plate should be moving to left side (due to pressure difference) or right side (as indicated by you to make contact with the cylinder)?