Pinned Boundary Countour

The graphical user interface of Elmer
Post Reply
Jorge
Posts: 3
Joined: 14 Oct 2019, 07:43
Antispam: Yes

Pinned Boundary Countour

Post by Jorge »

First of all I would like to congratulate you for the wonderful software that is elmerfem

I would like to do the exempel 3 of tutorialGUI but changing the cantilever beam model to the beam supported at the ends, allowing rotation in the plane of the beam. But among the documentation I can't find the parameter for it.

Model
BoundaryCondition
Name = Pinned
Linear elasticity
Displacement 1 = 0.0
Displacement 2 = 0.0
Displacement 3 = 0.0


Would i add something like it

Model
BoundaryCondition
Name = Pinned
Linear elasticity
Displacement 1 = 0.0
Displacement 2 = 0.0
Displacement 3 = 0.0
Rotation 1= 0.0
Rotation 2= 0.0
Rotation 3= Logical True


I am new with elmer (i began with elmer 3 days ago looking into documentation atm)
Regards.
raback
Site Admin
Posts: 4812
Joined: 22 Aug 2009, 11:57
Antispam: Yes
Location: Espoo, Finland
Contact:

Re: Pinned Boundary Countour

Post by raback »

Hi Jorge

There is a rather recent "TimoschenkoSolver" for "One-dimensional Equations for Elastic Beams", see Ch. 10 in current version of Elmer Models Manual.

There are also two consistency tests for the beam solver names Beam_3D_Cantilevel*.

Now the bad thing is that there are no XML files that make the menu structure for ElmerGUI. Usually this would not be too difficult to write but ElmerGUI comes with the limitation that it is designed to treat only 2D and 3D objects. Hence it is not possible to accomodate the 1D beam solver with that. Note that the reference 3D in the beam just means that the coordinates that define the beam may be set in 3D coordinates while the beam itself is still 1D object.

-Peter
Jorge
Posts: 3
Joined: 14 Oct 2019, 07:43
Antispam: Yes

Re: Pinned Boundary Countour

Post by Jorge »

Thank you Peter for the execelent explication.

TimoshenkoSolver looks really nice, the only thing that is going dificult understad to me, it is how the real value for Theta BC should be indicate to simular rotation in the extrem boundaries, because if we set the displacement U1 = 0.0, this contour condition is stable but when setting θ at the end of the contour to allow rotation, this value is variable and dependent on the type of load for the given model. Or it would simply be enough to set a binary logical value 0 1 for rotation yes or no. Would it be necessary to approximate a real value provided from the first derivative of the elastic dy/dx for a certain model.

I understand the 1D model, and that if you set a complete lateral contour preventing displacement on an axis, these contour cannot rotate because it is immobilized throughout its surface. I will try as soon as possible to make a test with the followwing model:

Create 3 bodies: Beam with 2 holes at the ends and located at the point that would represent the turn + 2 circular bodies (at the ends) in contact with the beam and apply a contour condition type "Slide Contact Logical True" as contact between the surface Then I would set the boundary conditions of the circular auxiliary bodies in the 3 directions with a value of 0.

Thank you very much for your time and sorry if I misunderstanding something. I apologize for my english (I am using google translate as an auxiliary help)

Regards.
raback
Site Admin
Posts: 4812
Joined: 22 Aug 2009, 11:57
Antispam: Yes
Location: Espoo, Finland
Contact:

Re: Pinned Boundary Countour

Post by raback »

Hi Jorge,

I'm not too familiar with BCs never having used to solver myself. I'll point this thread to the author of the module.

I do know that the contact conditions would not work as they are currently limited to 2D/3D problems. The general soft limiters might work. They differ from contact conditions by that the contact line must be known a priori.

-Peter
kevinarden
Posts: 2237
Joined: 25 Jan 2019, 01:28
Antispam: Yes

Re: Pinned Boundary Countour

Post by kevinarden »

Rotation at the ends means the DOF are free, that is to say there is no boundary condition. If you want a beam pined at each end then you would only assign displacement boundary conditions on the ends.

In the model manual Chapter 10 the boundary conditions are U and Theta, so a pinned beam would be

Boundary Condition 1
Name = Pinned
Target Nodes(2) = node labels of end nodes
U 1 = 0.0
U 2 = 0.0
U 3 = 0.0

Note that the beam would be free not rotate about its own axis which is a rigid body mode. So if the beam is along the X axis

Boundary Condition 1
Name = Pinned
Target Nodes(2) = node labels of end nodes
U 1 = 0.0
U 2 = 0.0
U 3 = 0.0
Theta 1 = 0.0

would be better.


Boundary Condition bc id
The Dirichlet conditions for the components of u and θ can be given in the standard manner. Note
that here the components of both vectors are defined with respect to the global coordinate frame.
U i Real
If the default variable name is used, then, with i=1,2,3, Dirichlet BCs for the components of
the displacement u can be given.
Theta i Real
If the default variable name is used, then, with i=1,2,3, Dirichlet BCs for the components of
the rotation θ can be given
Jorge
Posts: 3
Joined: 14 Oct 2019, 07:43
Antispam: Yes

Re: Pinned Boundary Countour

Post by Jorge »

Thank you Peter and kevinarden this clarified my doubts, it was simply that i don't need add the parameter except if i want block some of DOFs or block them in a determinated "grade" fixing the real value.

Excellent support and excellent sofware.!!

Thank you again.
Regards.
Post Reply