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contact-convergence problem-Please help me

contact-convergence problem-Please help me

contact-convergence problem-Please help me

(OP)
Hello
I am modeling an underground opening. the model is composed of three rock layers, the coal layer where i made the opening. This coal is sandwitches between two strong sandstone layers .

There is a contact between the coal layer and the other two sandstone layers. the model is elastic. only 0.64 of the job was completed and i got an error message.

I used job diagnostic tool to check the model i found that the top and the bottom layers penetrate the coal layers. these are the warning messages that i got?

Displacement increment for contact is too big.

Displacement increment for contact is too big.

Excessive distortion at a total of 35 integration points in solid (continuum) elements

Excessive distortion at a total of 2 integration points in solid (continuum) elements

Excessive distortion at a total of 2 integration points in solid (continuum) elements

Displacement increment for contact is too big.

Excessive distortion at a total of 27 integration points in solid (continuum) elements

Displacement increment for contact is too big.

Excessive distortion at a total of 131 integration points in solid (continuum) elements.

please help me.

Thanks

RE: contact-convergence problem-Please help me

Try applying a small initial time step, add in *contact controls, automatic tolerances, and stabilize and failing that apply an initial displacement in a dummy step to push the surfaces together before removing that in the next step.

RE: contact-convergence problem-Please help me

(OP)
Hello Corus, I know how to apply Contact control, however i need your help to

1- apply the stabilize and fail to apply dummy displacement to push the surface together.

2- apply the automatic stabilization.

Sorry if i ask you for more explanation, sometimes when i read the manual i can not understand, so your explanation is highly appreciated.

Thank you.

RE: contact-convergence problem-Please help me

(OP)
Hello Corus, that is what i did, please let me know if i did something wrong.

I added a dummy step before the main step, i did not apply load in that step, it is just to force the surface to be in contact. Correct?

I used *contact control and enhanced mesh to overcome the distortion. the model reaches equilibrium, thank you.

However i see that the master surface penetrate the slave surface. This affect the model results, do you how can i eliminate that penetration. i tried very fine mesh, but it did not work.

Your advice is highly appreciated.
Thanks.

RE: contact-convergence problem-Please help me

Try and have compatible meshes between the two contact surfaces to prevent penetration, or alternatively repeat the contact definition but swapping the master and slave surfaces in the second definition.

RE: contact-convergence problem-Please help me

(OP)
What is compatible mesh, Does it mean that both the master and slave should have the same element size?



I do not know how to swap the master and slave surface? could you please explain more? Thanks

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