# Help in defining a contact problem for multiple bodies

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### samyak jain

Jan 11, 2017, 5:49:37 AM1/11/17
to sfepy-devel
Hello everyone,

I am new to Sfepy and to Finite Element Analysis. I am currently trying to solve a contact problem between two bodies to the find the displacement and the stress.
The first body is a hemisphere (could be other shape-later on) and the second body is any free-form shape.
The second body is fixed and there is a specified displacement boundary condition on the first body.
That is all regarding the problem definition and the boundary conditions.

I have seen few examples in the gallery section sfepy website and I found an example of Contact Sphere, Contact plane and an example with displacement boundary condition.
But in all these examples, there is always one mesh and consequently one domain where we can define our boundary regions and solve the PDE.
But in my case, I have two mesh as I cannot combine them. If I can combine them as one mesh, I can solve the problem but I cannot do that.

So, how would I progress with this problem. I have two mesh, so I will have two different domain and them use it to define regions. Now the problem arises where should I define the field variable. What I understand that there will be two different field variable based on two domain but I am not sure how to use sfepy to solve such a problem.

Could someone please guide me by an example of such a case where contact between multiple bodies is done with multiple mesh being used. I have tried and I am unable to come up with a proper way to use sfepy with this problem.

Thanks a lot.

Samyak

### Robert Cimrman

Jan 11, 2017, 6:49:49 AM1/11/17
Hi Samyak,

sfepy does not support contacts of several deformable bodies yet and it is a
difficult thing to implement properly.

r.

### samyak jain

Jan 11, 2017, 6:58:24 AM1/11/17
to sfepy-devel
Hi Robert,

Thanks a lot for the reply. So I guess it is not possible to do that with general case of two bodies.

Do you think I can use ContactSphere to do that as one of my object in two bodies contact problem is an elastic sphere.

Samyak

### Robert Cimrman

Jan 11, 2017, 7:25:13 AM1/11/17
Hi Samyak,

On 01/11/2017 12:58 PM, samyak jain wrote:
> Hi Robert,
>
> Thanks a lot for the reply. So I guess it is not possible to do that with
> general case of two bodies.

No.

> Do you think I can use ContactSphere to do that as one of my object in two
> bodies contact problem is an elastic sphere.

It would be just a crude approximation, as ContactSphere is fully rigid. But of
course, you can try modifying the example with the ContactSphere to use your
mesh and see what it does. But that IMHO does not solve your original problem.

r.