Effect of RBE3s on stiffness

exx077

Hello,

 

If I am to put RBE3 in a hole (with no force or constraint attached to the dependant node) will this imply any stiffness to the voids outer surface where the independent nodes are?

Or does the hole just remain as it would if it was a void with nothing in it?

 

 

What type of 1D element could be used to provide a defined stiffness to the outer surface of a hole?

 

Thank you in advance

Q.Nguyen-Dai

RBE3 element has NO stiffness.

If you wan to add stiffness, try rod,bar, beam,...

tinh

are you continuing this topic?

https://forum.altairhyperworks.com/index.php?/topic/23230-contraining-a-hole-as-a-void-that-will-not-expeirence-deformation/

 

I suggest you try modeling a shaft and make it contact tied with hole of bracket

Sanjay Nainani_20973

Hello,

 

If you have particular stiffness values you want the hole to have, you can also try using GAP elements or CBUSH.

 

exx077

Hi all,

 

Thank you for your responses. This has helped with my understanding.

 

Altair Forum User said:

I suggest you try modeling a shaft and make it contact tied with hole of bracket

If I am to try to model a bearing I will use this method.

 

Altair Forum User said:

If you have particular stiffness values you want the hole to have, you can also try using GAP elements or CBUSH.

I do have a radial stiffness value. I will try and use these elements and input the stiffness values. Is it possible to use CBUSH or GAP elements as a spider that is constrained in the middle (like a RBE2 or 3 element spider)?

 

Thanks

tinh

try it! you can use cbush spider but i think no need to constraint its center

exx077

Hi @tinh,

 

I did try both methods.

The panels for spring and bar elements do not have an option to create a 'calculated node' from nodes selected on a surrounding face - like there is with the rigid and RBE3 element panels.

Hence, my question was, is it possible and if so, how?

 

Thank you

 

 

tinh

Just create the center nodes and bind it to hole by spring/bar

Sanjay Nainani_20973

As @tinh said create a center node.

 

You can do it by Geom>>distance.

<?xml version="1.0" encoding="UTF-8"?>

Select three nodes of circle and click on circle center

 

exx077

Hello,

 

Thank you for your responses. I will create the centre node using this method.

However, is it possible to select all the surface nodes on the inner surface of the hole in one go?

As from what I can tell I will have to select each node individually and connect this to the centre node to create a spider.

 

Thank you

tinh

there is a tcl script that changes rbe spider to bar/spring spider. I remember someone asked for it on this forum.please search it

exx077

Thanks @Tinh,

 

I came across this, but it seems to just be available to Altair clients - which I am not.

https://forum.altairhyperworks.com/index.php?/topic/13205-hyperworks-script-exchange/

 

Is there a better/easier way to add a defined amount of (radial) stiffness to a cylindrical hole?

 

Thank you

tinh

make a cylindrical system, assign it as disp system of the nodes and constraint their 1st dofs (r)