Multiple layers with frictional sliding in between them

[satyasrinivas]

Hi,

I have been trying to develop a 2 layered large scale model for geological applications. Due to the nature of the problem, I have to define contacts (10) between all surfaces that can come in contact with one another during the analysis.

When I run the model, it runs just fine for upto t = 0.08 (of a total of 1 unit) and the time increments begin becoming vanishingly small from this point forward. I tried my best to remove any over-constraints, but I cannot understand what is causing the problem.

I am attaching the cae file. Can somebody please suggest to me what may be wrong and if there is a more elegant way to define the contacts.

Thanks in advance
SS

 

[rstupplebeen]

Combine Left Gt on Gt and Lest Sst on Gt together. Do a similar methodology for the other cases. Both lefts could contact both Mains. I think the analysis is failing because your parts are sliding off of the defined contact. Also, the mesh is very coarse. You might want to look into refining it. I hope this helps.



Rob Stupplebeen

 

[rmettier]

Don't know if this helps, but I've had similar problems with large scale models, and it was also due to the sliding conflicting with the interaction definition. In the interaction definition you have define that there can be now seperation after contact. Now if a corner node of a surface slides off another surface, that would be seperation after contact, so it stays in conatct, resulting in wierd and extreme deformation and huge unrealistic stresses.
In my case, I managed to avoid the situation by allowing seperation and holding the contacts together with 'tie' constraints. Hope that helps.

And completely unrelated: I looked at your cae file, and I'm wondering where you got the nice tabular data for the plastic behaviour of the granite and sandstone. Your own measurements? Some citable source?

 

[satyasrinivas]

Thanks Rob and rmettier !

I will try both your suggestions and see what happens. I will update the status on this thread.

Rmettier,

The elasto-plastic hardening values for Granite and Sandstone are from published articles. These are for testing my models only;

Here are the references

Sandstone : *Zhu, W., Montési, L. and Wong, T.-f. (1997) Shear-enhanced compaction and permeability reduction: triaxial extension tests on porous sandstone, Mechanics of Materials, 25, 199-214.
( I have included volumetric strains from this paper in my model - if you have any suggestions as to how I can do it, please let me know)

Granite: Tullis and Yund, 1977. J. Tullis and R.A. Yund, Experimental deformation of dry Westerly granite. Journal of Geophysical Research 82 (1977), pp. 5705–5718