CBUSH Element with Nonlinear Property

seyilmaz

Hello every one,

 

I have created a demo model (all dofs are constrained at bottom and upper side allowed to move in vertical direction and rotations are free as well) to understand the characteristics of CBUSH element nonlinear properties. When I load my structure with 3484 N I get 1.71 mm displacement but increasing the load increases the displacement. Here are some screenshots: 

 

 

Thank you very much for your replies. 

 

Regards,

Adriano Koga_20259

This is nice for people who need an example. You should share this model here as a reference.

 

It is also very common to add a 'stopper' by adding a very large force as the last point, with a very small delta U, so that after this point the spring doesn't extend any further.

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seyilmaz

Dear Adriano,

 

Thank you for your answer. My real model is much more complex with couple of more Cbush elements carrying a large system that is exposed to acceleration forces, so I am not sure if your suggestion would work as I dont know how much force is distributed for each Cbush element. What I need is that each Cbush element carries different load values with a maximum deflection. Can you be more specific please?

 

Thank you.

Adriano Koga_20259

Tou don't know the stoffmess of each spring?

 

For different stiffmesses, you need different pbush card for each different spring.

 

I'm sorry, I actually didn't get your question.

seyilmaz

Actually what I am trying to model with TABLED1 is the stiffness of the elements. In my example I  expect maximum displacement of 1.71 mm but that is not the case. 

Adriano_Koga

if you look at your table, for both 1.71 and 50mm the force needed is the same, 50000.

This means that for any force that achieves this value, the displacements would be large.

 

I believe you are looking for a stopper like behavior, like i'1ve suggested before.

So your table would be:

 

...

1.71           50000

1.711         10000000(large number)

 

So that for anything above 1.71, the spring force is very large, keeping the displacement at this level.

FaroukM

Hi @seyilmaz

 

Can you please share the fem file.

 

Thanks

Martina Blazheska

I have a question kind of related to this: Can I use CBUSH elements in an NLSTAT analysis? If yes, can it be done with just defining the K-line?

Adriano_Koga

Martina Blazheska said:

I have a question kind of related to this: Can I use CBUSH elements in an NLSTAT analysis? If yes, can it be done with just defining the K-line?

i believe this was already answered in your specific topic here:

https://community.altair.com/community?id=community_question&sys_id=4bf3e66597fd3954e3b0361e6253af78

 

Ans a good Knowledge Base shared by @Vinicius Gomes  there.