Constraints on contact surfaces?

[Bigtree]

Hi, I have two contact surfaces(Master-slave) with normal-Hard and tangential-Rough interactions.
How can I constrain them or I shouldn't? (pin-contact problem)

 

[corus]

Why should you constrain them?

corus

 

[Bigtree]

Hi, actually I am confused of this. For between the mechanical contact surfaces(Master&Slaves) I applied Tangential and Normal contact properties, I suffer "Too many attempts and then it aborted". Both surfaces are semi-circular(deformable and discretized rigid)
Sometimes, the job is completed if I didn't constrain the two contact surfaces and sometimes it just aborted.

 

[corus]

Look in the msg file to see how many points are opening and closing at each iteration. If it's just one or two then use the contact controls card. Also, don't use quadratic elements.

corus

 

[Bigtree]

Hi, Thanks.Two materials were combined together with a center hole.A rigid pin was through the hole with concentrated forced on reference point.
Initial step:converged
Step 1:Converged. (To establish contact among surfaces)
Step 2. Not conveged after several increments.

I already refined the meshing, decreased the initial increments(0.1), and used the contact controls. It sitll couldn't converge.
Error message:too many attempts. 0 pivot.over constrained.

 

[corus]

Over constraint usually implies that the contact surface has restraints applied to it. A zero pivot, however, usually implies you haven't enough restraints and the matrix is not positive definite. Check your restraints to see if you're not conflicting with the direction that contact occurs.

corus

 

[Bigtree]

Hi, thanks.
Error messages:
Time increment required is less than the minimum specified
Should I make it smaller (1.E-6)?