Constraint and load about a ring calculation to make it to a specific deformation

Yvette Lian

Hello all,

 

I'm trying to calculate a ring deformation. In this calculation, I get the specific deformation of the ring. As you can see from  , I want to give a circumferential pressure using the hoop to make it smaller and then the gap can be closed. I want to know how much force or pressure I need to use to get the deformation so I need to have a try. Then several questions come to me.

 

1.How to constrain? If I don't give the constraint, the ring will move to infinity. I don't know which way is best for this situation. Also the hoop should be considered in the constraint.

2.How to give the load? As the hoop is more narrow than the ring width in z direction, it contacts the ring at the middle with 25mm width. I use pressure applied in the contact surface. As the gap exists, the deformation will be non-uniform under stress. But the pressure is always uniform, is pressure suitable for the fact?

 

For your convenience, I attach the example here.

 

Thank you very much!

 

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Altair Forum User

Hi @Yvette Lian

 

Which solver are you using for the analysis?

Yvette Lian

Hi @Prakash Pagadala,

 

I use Optistruct for it.

Altair Forum User

You can start by creating a cylindrical coordinate system and assign the spcs in the same. But make sure to release constraint in the direction of contraction which will be radial direction...

 

 

Yvette Lian

Hi @Prakash Pagadala,

 

Thanks for your quick reply.

 

I could create a cylindrical coordinate system. But I don't know how to define the SPCs correctly. In the constraints panel, I could only constrain dof1-6. But it seems not suitable for the cylindrical coordinate. So how should I define the constraints? And where should I define? Do you have any examples? 

 

Thanks a lot!

Altair Forum User

HI,

 

Please see the image below. In the systems panel go to ASSIGN>> Change to loads and select the system and click assign,

 

The XYZ in cartesian is R, theta, and Z of the Cylindrical system. Based on this you can constrain the model. 

Yvette Lian

That' great ! So according to the hoop, I should constrain Z and t and release r for the circumference contact surface, is it right?

 

Also, about my question 2, do you have any comment?

2.How to give the load? As the hoop is more narrow than the ring width in z direction, it contacts the ring at the middle with 25mm width. I use pressure applied in the contact surface. As the gap exists, the deformation will be non-uniform under stress. But the pressure is always uniform, is pressure suitable for the fact?

 

Thanks a lot!

Altair Forum User

Hi,

 

Let me try with on your model and I will get back to you. 

Altair Forum User

HI,

 

Can run this model?

 

I had randomly applied an enforced motion 

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Yvette Lian

Hi @Prakash Pagadala,

 

Thanks for your response. I've run your file, but still confused with several parts.

 

1.Why you constrain in all DOFs?  If constrain 1,2,3 is enough for this hoop situation?

 

2.And should I need to apply enforced motion for my case also?  

 

Thanks for your patient answer!

Altair Forum User

Altair Forum User said:

1.Why you constrain in all DOFs?  If constrain 1,2,3 is enough for this hoop situation?

 

I have enforced displacement in the radial direction and it requires an SPC in the same Dof

 

Altair Forum User said:

2.And should I need to apply enforced motion for my case also?  

 

Since I don't know the magnitude of the pressure to apply, I started with enforced motion. You can refine the model with the desired load and also you may have to create contact between the gap. 

Yvette Lian

Hi @Prakash Pagadala,

 

I understand what you mean during your bdf file. Thanks!

 

Also, I recalculate my file. First I use the previous file to get a relatively reliable pressure value 0.002MPa to the contact surface to get a deformation. Then I use the same pressure on the file using cylindrical coordinate system and constrain 2,3 of t and z.  But the result seems not ideal. It almost has no deformation. If I make the wrong constraint?

 

I attach the two files of my calculation I mentioned. Could you please help me find the mistake? 

 

Thanks again for your help!

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Altair Forum User

Hi,

 

If you are using pressure or load, you may have to release the radial Dof.

Yvette Lian

OK I get it!

 

Thanks for your always patient answer !