I am getting started to FEniCS, and I have a few time to implement my method. I want to do a structural analysis (fem) of a mesh that I am generating with mshr and dolfin. It’s a 3D lattice structure (photo attached), the boundary condition is [displacement in y==0] = 0 and it has a punctual force…

Post a MWE and the complete error message.

[image] Thiago: As @volkerk says, please post a Minimal working example and the full error message. However, I think your boundary condition should be: bc = DirichletBC(V.sub(1), Constant(0), clamped_boundary) Is this enforces a zero deformation condition only in the y-direction (sub-spac…

I tried to remove the force and apply 2 boundary conditions, which the second one (top) is to simulate the effect of a load. E = Constant(1e5) nu = Constant(0.3) mu = E/2/(1+nu) lmbda = E*nu/(1+nu)/(1-2*nu) def eps(v): return sym(grad(v)) def sigma(v): return lmbda*tr(eps(v))*Identity(3) + 2*mu*…

As you have not supplied to mesh, I’ve changed the problem to a 2D problem. If you would like to to the point force (or any pointwise boundary condition), you need to remove the on_boundary argument from your topbc function, and add pointwise to the topbc. I’ve illustrated how to use a pointforce i…

Sorry, I forgot to show my mesh. It has around 772533 cells, so think that’s why the solver not working. It’s the same mesh I attached a photo before > # size of the mesh > X = 2 > # Y and Z are calculated from X and nx,ny,nz > > # number of cells in each direction > nx = 2 > ny = 2 > nz = 2 > …

Hi, try to make a 2D version of your problem to ensure you are solving the problem in the correct fashion before doing a huge computation. To apply bcs on a full plane, you do not Need an additional argument, as you are applying the condition to more than one point.

Hello I have implemented your suggestions in 3D cantilever to apply pointforce at the free end in adition to body force but the displacement value I get is not like I expected. There must be a mistake how can I fix this? from dolfin import * from ufl import nabla_div # Load mesh and define functio…

You should apply bc_p to the variational problem, as you do with bc_base.

Thank you, I have tried this commnet below it but there is no change in displacement. solve(a == L, u, bcs=[bc_base,bc_p]) I had implemented your example above in January 31.For the one with pointforce, you did not provide bc_top = DirichletBC(V.sub(1), Constant(desloc_top), topbc,“pointwise”) t…

This is because you were mixing in tolerance inside your subdomain definition, using near and 1-tol. The following code works. from dolfin import * from ufl import nabla_div # Load mesh and define function space L = 10. W = 1. # Mesh for cantilever beam Omega = BoxMesh(Point(0, 0, 0), Point(L, W,…

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variational formulation

dokken April 8, 2020, 7:32pm 24

I am gonna stop replying to you, as you are clearly not putting in any effort to solve this yourself. I have already shown you how to do this in Applying a force on a face

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