NON Convergence with CBUSH and RBE 2 Connection

Ashish_MEXPERT

Hello all,

 

I am solving currently non-linear static problem. I have continue Non-Linear Convergence problem. For analysis i have used RBE2 and CBUSH elements. The problem i am facing with the situation to deal with constraints and load at only one node. 

 

I have attached the File where you can see the situation in the model.

 

I have RBE2 elements (GREEN) which are connected to 2nd Order Solid Tetra mesh and over which force needs to be applied. The same independent node of RBE2 is connected to CBUSH elements (Orange) left and right with K-line 1-6 blocked with two nodes left and right which are 1-3 DOFs blocked down. 

 

I have Loads need to be applied in different directions with different local co-ordinate systems, so for this i have applied CBUSH with Zero-Length defined in Local Co-ordinate Systems and made it free in the direction where force is to be transfered and it is connected to RBE2 Independent node and with SPC - Node at which the Force is applied . Now force can be transferred according to directed by CBUSH elements in different Local C-ordinate system to the elements Solid Tetra Mesh. 

 

But with this mechanical concept i am having Non-Convergence solution, is there any other way or any other solution i can apply on RBE2 element so that i will be able to apply loads in different local-cordinate systems at the same node ?

 

Thanking You !

 

BR Ashish

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Altair Forum User

Hi @Ashish_MEXPERT

 

Is it possible to share the model file with us please?

 

You can share using file transfer link which is available in my signature. 

Ashish_MEXPERT

Hi Prakash i have sent you the file, please have a look ??

 

 

Thanks !!

 

Regards

Ashish

Ashish_MEXPERT

Hi Prakash,

 

I think i found where the problem is. Its the problem of contact seperation between the cylinder and the surface where slanting cylinder is in Sliding Contact.

 

So how can i solve the contact seperation problem ? The condition is i need to have sliding contact between slanting cylinder and surface how can i restrict both the surfaces in this case so they cant fly each other.

 

Thanks ! and Regards

Ashish

Altair Forum User

Hi Ashish,

 

DIdi you try with Stick instead of Slide on Contact card?

 

Please try and check if this helps. 

Ashish_MEXPERT

Hi Prakash,

 

I have used stick option now i have less Displacement values but still having large Nonlinear EUI values and Contact closed decreases to 0. How can i make it stable ?

 

Thanks !

 

BR Ashish

Altair Forum User

Hi Ashish,

 

Is it a large displacement problem?

 

Can you try with NLSTAT with LGDISP?

Ashish_MEXPERT

Hi Prakash,

 

Ok how to define it in the model properly LGDISP case ??

 

Because i have used it in control card this option but my solver is crashing down without showing any reason.

 

Can you please explain  ??

 

Thanks !

Altair Forum User

Hi Ashish,

 

goto control cards>> PARAM>> LGDISP>>1

 

Now go to loadsteps>> NLSTAT and instead of normal NLPARAM, use NLPARAM(LGDISP) and refer the NLPARAM here. 

Ashish_MEXPERT

Hi Prakash,

 

I have used it as u said but its error giving ,

 

' MORIENT should not be OPENGAP or OVERLAP for finite sliding CONTACT 83. '

 

I did NORM for that contact and then this option doesnt starts claclualtion my solver is crashed down.

 

Thanks ! and Regards Ashish
 

Ashish_MEXPERT

Hi Prakash,

 

This is actually not the LGDISP problem so it doesnt make sense to apply it over here in my problem. 

 

Can you tell me if EXPRT CNTSTB works for contacts ? and how to setup correctly that with values of parameters ?

 

Thanks !

Altair Forum User

Hi Ashish,

 

You can use EXPRT Contact stabilization using PARAM>> EXPRTNL>>CNTSTB.

 

Could you please share the .out file just to check if there are any warning written?