contact problem in abaqus

[faadam]

hi all,

I am new in Abaqus. I am using version6.10. I have been working on a model, but I am stuck. Here is my model. I have a concrete slabs and a base(soil). concrete is on the top of soil. And There is pressure a portion of the top slab(square load at the edge) and elastic foundation on the bottom of base part.

dimensions: 38000 by 38000
thickness of base=150
thickness of slab=250
elastic foundation=0.3
concrete elastic modulus= 28000
base elastic modulus= 5000
Poisson ratio is 0.2 for all


when I tried to find the pair of contact and tied them, it worked perfectly. however when I assign an interaction property(frictionless for my case) it keeps giving error and warnings ( Too many attempts made for this increment & Displacement increment for contact is too big.)
I am suspecting I am making a mistake in STEP part . Can anybody help me out with how to set a frictionless interaction property between two concrete slabs while there is a elastic foundation and a a downward presure?
fatih

 

[StefCon]

Hi,
What kind of contact are you using? I'm a bit confused of the word "tied" since there is something called tie-contact. When you remove the friction, the upper slab (or the lower) doesn't have any constraints in the contact plane. It will slip off and thus the model never converges. If this is the case, just add a boundary conditions saying =0 along the axles that span the contact plane.

Hope it works,
Regards,
S

 

[faadam]

Hi stef,

for the first time i used tie-contact between the bottom upper slab and the top of bottom slab. and there is only elastic foundation at the very bottom(bottom of bottom slab). i applied a square load(pressure) to simulate a tire on the slab.
this model worked. but when i changed the 'tie-contact' to frictionless to simulate the situation which they are independent, the model didn't work. i didn't think they will slip coz i applied the load downward. i tried with all kind of BC but it's started running forever. i attached the script file if you can look at it and let me know where my mistake is i ll will appreciate it.

thanks for your help.

fatih

 

[StefCon]

Hi,
I cannot see what is wrong by looking at the file. All I see is that your run did not converge.
Try giving it a friction of 0.1 just to find the error. If 0.1 works then your boundary conditions are probably faulty.

What tie-contacts do is glue your slabs together. So before it couldn't fly away. Try giving all components a surface each with a boundary condition that constrains all translations and rotations (from step 1 to the last) just to see if it works.

I usually break up my models in a lot of steps so I know exactly what didn't work.

Good luck,
S