Search found 155 matches

by mika
13 Apr 2020, 11:40
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

Is this 6 constraints? Spring 5 = Real 4.019e3 U 2 = Real 0.0 U 1 = Real 0.0 U 3 = Real 0.0 DNU 4 = Real 0.0 DNU 6 = Real 0.0 These six constraints do not prevent rigid body rotations since only three constraints are given for the translational DOFs (in this case they are U 1, U 2 and U 3). Constra...
by mika
12 Apr 2020, 15:57
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

To prevent (infinitesimal) rigid displacements (c1,c2,c3) + (b1,b2,b3) x (x,y,z) = (c1,c2,c3) + (b2*z-b3*y,-b1*z+b3*x,b1*y-b2*x) of the shell mid-surface one should give at least six constraints for the translational DOFs of the shell model. Constraining DOFs which are associated with the directiona...
by mika
10 Apr 2020, 12:21
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

Your shell model is not sufficiently constrained to prevent rigid-body motions as there seems to be a pointwise constraint in one node only. The negative eigenvalue is an approximation of zero. Zero eigenvalues are associated with rigid-body motions.

-- Mika
by mika
09 Apr 2020, 13:46
Forum: ElmerSolver
Topic: Turbulent Flow Simulations with Elmer - A Request
Replies: 19
Views: 1905

Re: Turbulent Flow Simulations with Elmer - A Request

If the mesh contains prisms or pyramids, at the moment the value of the keyword "Stabilization Method" must be defined to be some other string than "bubbles". If bubble functions were wanted for stabilization purposes, one could try to use for example Stabilization Method = String "p-bubbles" Elemen...
by mika
03 Apr 2020, 17:53
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

I modified your sif somewhat and see a mass to change results. I also mention that to get eigenvector output it's better to forget the (default) component names of the shell solver variable and use a single name for the entire solution. This has also been done in the attached file.

-- Mika
by mika
01 Apr 2020, 15:05
Forum: ElmerSolver
Topic: Structure Analysis with both Beam and Shell elments
Replies: 16
Views: 1432

Re: Structure Analysis with both Beam and Shell elments

I will try to make a first look at the necessary amount of coding within a couple of weeks, say. If the implementation turns out to be more complicated than expected, this may change to be a longer-term goal.

-- Mika
by mika
01 Apr 2020, 14:39
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

I updated the utility SpringAssembly so that a localized (generalized) mass can be added in a similar way as a spring. The keyword is "Mass k", k=1,2,... . By physical reasons the values of "Mass 1", "Mass 2" and "Mass 3" should be the same for 3-D displacements as they represent the same scalar qua...
by mika
27 Mar 2020, 20:00
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

Does the target boundaries also work so if there were many nodes each node would not have to be listed? After a fresh update of the shell solver it should also be possible to add spring BCs by using the keyword "Target Boundaries", for example Boundary Condition 4 Target Boundaries(2) = 5 6 Spring ...
by mika
26 Mar 2020, 23:29
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

Thanks for testing, The variable of shell solver is by default specified as Variable = Deflection[U:3 DNU:3] Since the sif file now specifies Dirichlet BCs in terms of the component name U, one shouldn't define a different variable name in the solver section 1. That is, the line "Variable = Displace...
by mika
25 Mar 2020, 19:20
Forum: ElmerSolver
Topic: Introducing springs to a point/face as a boundary condition
Replies: 62
Views: 3094

Re: Introducing springs to a point/face as a boundary condition

Hi, The nonlinear elasticity solver has now been fixed so that point elements are no more skipped in the matrix assembly. Giving a spring constraint should thus work if the target nodes define entities in the mesh file mesh.boundary as mentioned earlier. Specifying the places of springs using the ke...