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Shell-solid interaction

Posted 23.07.2012, 13:03 GMT-4 Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 4.2a 7 Replies

Rachel Westwood
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I am trying to solve a basic model, whereby two (or more) identical hollow shell cylinders (columns) of 2m radius and 30m height with a mass on the top are placed on a solid cylinder with dimensions of 50m radius and 20m depth. I am running an eigenfrequency analysis and would like to see how both cylinders vibrate and how they interact if I put more force on one column than the other.

I have set a prescribed displacement of the contact edge on the base of both cylinders in the solid domain equal to the displacement values (u,v and w) in the shell domain.

Instead of seeing just one frequency on running the eigenfrequency analysis, I see two identical frequencies for each column. This doesn't show how and if the columns are interacting with each other at that frequency. Ideal I'd just like to see one frequency with both columns bending (if thats the case) and the ground cylinder reacting accordingly.

Can anyone help? I hope that makes sense.
7 Replies Last Post 28.11.2012, 10:43 GMT-5
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 23.07.2012, 14:06 GMT-4
There could be something wrong in the way you define the coupling between the 2 shells and the solid cylinder. That can cause no coupling and hence the separate eigenmodes.

Nagi Elabbasi
Veryst Engineering
There could be something wrong in the way you define the coupling between the 2 shells and the solid cylinder. That can cause no coupling and hence the separate eigenmodes. Nagi Elabbasi Veryst Engineering
Rachel Westwood
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Posted: 1 decade ago 24.07.2012, 06:26 GMT-4
Hi Nagi, thanks for your reply. Please could you explain a bit further? I have added a prescribed displacement constraint on the base edge of the two columns in solid mechanics physic and set the value equal to the displacement values of the shell physics (u, v and w).
Hi Nagi, thanks for your reply. Please could you explain a bit further? I have added a prescribed displacement constraint on the base edge of the two columns in solid mechanics physic and set the value equal to the displacement values of the shell physics (u, v and w).
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 25.07.2012, 09:33 GMT-4
Hi Rachel,

Conceptually what you’re doing seems correct. What expressions do you use to set the displacements on the base edge to be equal to those of the corresponding shell edge? Do you use a mapping operator? You can also look at the displacement results to check if these prescribed conditions are setup correctly.

Nagi Elabbasi
Veryst Engineering
Hi Rachel, Conceptually what you’re doing seems correct. What expressions do you use to set the displacements on the base edge to be equal to those of the corresponding shell edge? Do you use a mapping operator? You can also look at the displacement results to check if these prescribed conditions are setup correctly. Nagi Elabbasi Veryst Engineering
Rachel Westwood
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Posted: 1 decade ago 25.07.2012, 11:10 GMT-4
Hi Nagi,

I have simply set a prescribed displacement on the edge with u2 = u, v2 = v, w2 = w. I'm not sure what you mean by a mapping operator, sorry. I have plotted a 2D line graph of the edge using solid.u2 and shell.u adn the graphs plot on top of each other. I've attached a model.

Thanks,

Rachel
Hi Nagi, I have simply set a prescribed displacement on the edge with u2 = u, v2 = v, w2 = w. I'm not sure what you mean by a mapping operator, sorry. I have plotted a 2D line graph of the edge using solid.u2 and shell.u adn the graphs plot on top of each other. I've attached a model. Thanks, Rachel
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 25.07.2012, 12:37 GMT-4
Hi Rachel,

Actually you have the displacement condition defined properly. I thought the shell and solid do not share the same geometry which would have required some kind of Model Coupling.

The reason you’re not seeing the coupling is that the solid is much stiffer than the shell and is fixed at most of its boundaries. I tried one variation where I reduced the solid’s modulus to 1 GPa and excluded Face 3 from the Roller 1 displacement condition and then I see the coupling clearly.

Nagi Elabbasi
Veryst Engineering
Hi Rachel, Actually you have the displacement condition defined properly. I thought the shell and solid do not share the same geometry which would have required some kind of Model Coupling. The reason you’re not seeing the coupling is that the solid is much stiffer than the shell and is fixed at most of its boundaries. I tried one variation where I reduced the solid’s modulus to 1 GPa and excluded Face 3 from the Roller 1 displacement condition and then I see the coupling clearly. Nagi Elabbasi Veryst Engineering
Rachel Westwood
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Posted: 1 decade ago 26.07.2012, 09:56 GMT-4
Thank you for your help Nagi. It's great to know I am on the right tracks. My next step is to add water above the ground going part way up the column to see how the vibration of the columns affects the liquid.
Thank you for your help Nagi. It's great to know I am on the right tracks. My next step is to add water above the ground going part way up the column to see how the vibration of the columns affects the liquid.
Tao Shulang
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Posted: 1 decade ago 28.11.2012, 10:43 GMT-5
Hello,I am working with a problem concerned about shell-solid interaction,I built a model (in the attachments), I want to calculate the eigenfrequency of this model ,but I am not sure whether it is reasonable,I donnot know whether I should add any conditions?
Hello,I am working with a problem concerned about shell-solid interaction,I built a model (in the attachments), I want to calculate the eigenfrequency of this model ,but I am not sure whether it is reasonable,I donnot know whether I should add any conditions?

Attachments:

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