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anbazhag
Posts: 12
Registered: ‎03-06-2012

Surface contacts not working

225 Views, 2 Replies
03-20-2013 08:57 AM

Forearm on ground

 

Analysis type: MES with nonlinear material models

 

 

I am modeling a forearm section on the ground, and applying loads to the top of the forearm to analyse the deformation.

I have set surface-contacts between the outer layer of the skin and the ground. However, when i run the simulation, the model penetrates through the ground and goes down.

 

I have assigned brick elements to all parts. The ground is made of concrete.

 

Can someone tell me why this is happening?

 

PS. I have also tried using an impact plane instead of the ground part. However, the forearm does not deform, and the simulation completes ina  minute, and the results show no changes.

 

Please help.

 

 

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*Expert Elite*
AstroJohnPE
Posts: 570
Registered: ‎08-30-2012

Re: Surface contacts not working

03-20-2013 06:27 PM in reply to: anbazhag

Hi anbazhag,

 

It is rather difficult to diagnose contact problems just by a description, so you may need to read the thread "Create, Post, or Provide an Archive of your model" and provide an archive of your model.

 

For the model with surface to surface contact, does the arm pass through on the first time step? If so, how far does it penetrate? If it moves too far on the first time step, the contact may not be detected. (Whether it is or not in contact at step 0, and if it is not in contact at step 1, then the software assumes that it is not in contact between steps 0 and 1.)

 

For the model with the impact plane, does no results literally mean that all results (displacement, stress) were 0? Was their a warning that said the model is on the wrong side of the impact plane? (That is, you can not push something against the ground if the thing is already buried!)

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

Simulation Mechanical user since Dec 1997
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Contributor
anbazhag
Posts: 12
Registered: ‎03-06-2012

Re: Surface contacts not working

03-27-2013 12:13 PM in reply to: AstroJohnPE

Hi AstroJohn,

 Thanks for your reply. I changed the no. of time steps from 20 to 100, and the simulation started working, as the contact surfaces were recognized. Thus, I didn't have the need to use an impact plane .

 

However, the simulation was taking a long time (about 20 hours) to complete 50%, since there were warnings. The warnings read distorted element *** in part 1, maintaining its integrity!

 

Is there a way to fix this problem? I read that changing the time steps, and refining the mesh could solve this issue. I did both.

 

I have uploaded the ACH file here: http://a360.co/YJfwwX

 

Thank you.

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