NL-Quasi-Static Analysis with Friction Contacts + Pretension not converging

Hello,

 

I am working on an non-linear-quasi static model with pretensioned bolts and friction contacts.

I set up the model with first order elements first, this model was converging fast and results were ok.

 

in order to get the correct tensions i changed the elements to second order.

After this i recreated the contacts and pretension to make sure everything is correctly linked to the second order elements.

 

If i run this model it is taking days and doing a few iterations until it starts all over again and again.

 

I use surface to surface contacts and a value of friction of 0,14.

I am not sure why this is happening because everything is the same as in the first order elements.

 

Could you please help? I uploaded the out. file and did a few screenshots.

 

Thanks a lot!

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

 

 

 

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