Dear Konstantinos
I shall be able to generate the obs array exteriorly
What do you mean by signed distance?
I often simulate organs that can move inside a 2D surface cavity
So the distance shall have always the same sign isn’t it?
I have worked a lot with level sets.
So the algorithm distance from a point to a surface (surface being defined by a triangle collection) I know it almost by heart
I could implement it in getfem
I am aiming to study the source code of getfem these next weeks
My principal investigator is requiring that I develop the competence to change getfem
So that there is no limit to what I can do
Just that I need to refresh my C++ with tutorials
Rigid contact is a way to start easy with mastering contact methods in getfem
However my ultimate goal is to be able to model contact between two 3D objects but I did not have any success with it
My python script lines are those 3 options
Option 1 generates a core file
Option 2 is not the correct syntax
Option 3 takes forever to converge and complains about tetrahedra orientation
optslcont=3
print(" optslcont ", optslcont)
if optslcont==1:
md.add_penalized_contact_between_nonmatching_meshes_brick(mimu3h, "uh", "ub", "penal_r", HEAD_BOUND, BRAIN_BOUND)
elif optslcont==2:
md.add_integral_contact_between_nonmatching_meshes_brick(mimu3h, "uh", "ub", "penal_r", HEAD_BOUND, BRAIN_BOUND)
elif optslcont==3:
release_dist = 1.
aug_factor = 0.1;
md.add_initialized_data('r', aug_factor * Muh * (3*Lambdah + 2*Muh) / (Lambdah + Muh) )
md.add_initialized_data('f_coeff', 0.)
md.add_initialized_data('alpha', 1.)
ibc = md.add_integral_large_sliding_contact_brick_raytracing('r', release_dist, 'f_coeff', 'alpha', 0)
md.add_filtered_fem_variable('multcontactb', mfub, BRAIN_BOUND)
md.add_slave_contact_boundary_to_large_sliding_contact_brick(ibc, mimu3b, BRAIN_BOUND, 'ub', 'multcontactb', '')
md.add_master_contact_boundary_to_large_sliding_contact_brick(ibc, mimu3h, HEAD_BOUND, 'uh', '')
Regards
Thank you
Anne-Cecile
From: Konstantinos Poulios <logari81@googlemail.com>
Sent: Monday, March 28, 2022 5:27 PM
To: Lesage,Anne Cecile J <AJLesage@mdanderson.org>
Cc: getfem-users@nongnu.org
Subject: [EXT] Re: rigid contact with arbitrary surface
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A good starting point for modelling contact in GetFEM is this example:
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.
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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