Re: rigid contact with arbitrary surface

[Konstantinos Poulios]

Dear Anne-Cecile

A good starting point for modelling contact in GetFEM is this example:

https://git.savannah.nongnu.org/cgit/getfem.git/tree/interface/tests/python/demo_static_contact.py

The special thing in your case is that you would like to have contact between a 3D solid and a 2D surface, which AFAIR is a case that is not directly available, but everything is possible.

For example if you are interested in small-deformation (i.e. linearized kinematics) then this is how contact is defined, in the demo I gave you above

   OBS = mfd.eval(obstacle)
   md.add_initialized_fem_data('obstacle', mfd, OBS)
   md.add_integral_contact_with_rigid_obstacle_brick(mim_friction, 'u', 'lambda_n',
                                                      'obstacle', 'r', GAMMAC, version-4);

In your case, "u" will be a displacement variable describing the deformation of the solid, "lambda_n" will be a scalar multiplier defined on the surface of the (deformable) 3D solid, mfd will be a scalar mesh_fem, defined on the same (3D solid) mesh as "u".

The only special thing for your case will be how you calculate the array OBS. This array must contain the (signed) distance of every node of (the 3D solid) mesh_fem mfd from your rigid 2D obstacle surface. AFAIR GetFEM does not have a convenience function for calculating the distance between points in a 3D solid mesh and a 2D surface mesh. The raytracing interpolation available in GetFEM allows only to calculate distances from the surface of a 3D solid to the surface of another 3D solid. So unless you find another way to calculate your OBS array, we will need to do some modification in GetFEM to make this easier.

Best regards

Kostas

On Mon, Mar 28, 2022 at 10:48 PM Lesage,Anne Cecile J <AJLesage@mdanderson.org> wrote:

Dear all

 

Is it possible in getfem to impose a contact with a rigid arbitrary surface defined by a 2D triangle mesh for example?

 

Regards

Anne-Cecile

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