NX NASTRAN Surface to Surface contact problem 1

[harshitbhatt]

Hello everyone. I am doing a problem where I have a cylinder and two plates.I need to find out the deformation of the cylinder.I have given the BC and also have given surface to surface contact to cylinder and the plates.



But when I run the simulation, the cylinder is penetrating the plates which should not happen.

Can any one please help me out.I have attached my .fem and .sim files for your reference.



Actually it should look something like this but for me its penetrating into the plates.

 

[Tuw]

Hi Harshitbhatt,

The picture you attached is showing exaggerated view.

Please refer link below for explanation.

https://community.plm.automation.si...-dialogue-box-of-basis-structural/td-p/289629

 

[harshitbhatt]

@Tuw thank you for the reply sir.

I have done the same but I dont get the result what I am expecting to be[The 2nd picture for example in the post].

Doing the same,it somewhat penetrates the other surface i.e. the cylinder penetrates the other plate.

 

[Tuw]

Hi Harshitbhatt,

To be able to deform a sphere into something that you shown in the 2nd figure, is quite a challenging issue.
Some of the consideration that need to be taken care of:

1. You need a realistic material data. You cant expect a plastic material to deform into the shape shown. Is that rubber?
2. Meshing need to be fine at that point of deformation. We cannot expect a huge Tetrahedral element to give you such a complex and unique shape of deformation. And even though it could give you, the element would have extremely bad quality that it is not accurate.
3. Probably the most important capability required for this analysis is the adaptive meshing, where the model would remesh itself whenever a certain mesh threshold value is achieved in order to maintain the mesh quality while be able to deform in such complex form. Unfortunately the current NX CAE cannot do that. I know LS Dyna with EFG capability should be suitable for this application, but again, it is not easy to achieve that.

Please find a video link to the example of LS Dyna 3D remeshing capability as below:

https://www.youtube.com/watch?v=hVf2RTzv2o0&feature=youtu.be

Tuw

 

[harshitbhatt]

@Tuw thank you again for your valuable reply sir.

Yes the material is plastic.

I have not done fine mesh as my device configuration is not more.When I do fine mesh it gets stuck.Stuck in the sense it takes very very long time.

I didn't got the 3rd point you wrote.

Thank you.

 

[Tuw]

Harshitbhatt,

I still dont think plastic could deform into such shape under pressure loading. But lets say it can, you need the stress strain curve for realistic deformation.

Fine mesh is required, because the particular deformation is fine.

About my 3rd point, is about the solver ability to remesh the simulation model during the solving process, in order to maintain the mesh quality due to complex shape deformation.

Regards,
Tuw

 

[harshitbhatt]

@Tuw thank you for the reply sir.

I will try with rubber and fine mesh.

But I have different pressure acting on cylinder.Upper surface has 20 bars and lower surface has 1 bar.I am giving this on each face of cylinder after meshing because if I select no filter than it selects whole cylinder.

So after fining the mesh it will have more faces and I need to give pressure on each and every face.So is there any way to give pressure like this so that I dont have to give on each face.

I hope you understand what I am trying to say.I have attached the figure for your ref.

Thank you for your valuable reply.

 

[Tuw]

Hi Harshitbhatt,

Simple. Divide the face accordingly during the CAD preparation step.
When trying to apply the loading condition, just apply at the polygon face (Choose polygon face at the selection filter).

 

[harshitbhatt]

@Tuw I am doing the same sir.

But when mesh is done fine,number of polygon faces also increases.