1D beam modelling

[mkheiri]

Hi all,
I would like to simply model and solve a 1-dimensional (1-D) beam (like a line) where one end is fixed and the other end free. I would like to obtain the deformation of the beam under a vertical force acting on the free end. I need to assign cross-sectional properties (like area, moment of inertia etc.) since I do not want to explicitly model the beam in 3-D. However, I am not sure if 1-D geometries and 1-D meshing are supported in Elmer or not. Could you please guide me? Many thanks.

Mojtaba

[kevinarden]

https://github.com/ElmerCSC/elmerfem/tr ... Cantilever

[amarfayyad]

https://github.com/ElmerCSC/elmerfem/tr ... Cantilever

Hi, Thank you very much. I am also working on similar problem. However, I couldn't successfully define a point load at the free end from a concentrated mass as in the 3D beam tutorial. This is what I tried in the given sif file.
! Node 1 is the fixed and Node 2 the free one. It's point elements at the boundary
Boundary Condition 2
Target Nodes(1) = 2
Name = "Mass"
Force 2 = -2.0e+3
End
Can you kindly help in this regard? Thanks a lot.

[raback]

Hi

It seems that Neumann conditions for this 0D entity have not been implemented. However, we are lucky in that for single nodes the integration rule is simple and you can equally well give, for example:

Code: Select all

Boundary Condition 1
!  Target Boundaries(2) = 1
  Target Nodes(1) = 2
  U 1 Load = Real 1.0
  U 2 Load = Real 2.0
  U 3 Load = Real 3.0
End

This would set force f=i+2j+3k to the selected node.

-Peter

[amarfayyad]

Hi Peter,
I verified it with the analytical solution and it works! Thank you very much.
-Amar

[amarfayyad]

Hi everyone, I have been trying to extend this work to do an eigen analysis on a 1D cantilevered beam. I tried to use a solver setting inspired by the eigen analysis of the 3D beam tutorial, eigen analysis of plate tutorial and also modifying Timoshenko Beam Equations solver posted by @Kevinarden. However, none of these worked. Then I tried the shell.sif file given in "Panel speaker simulation - harmonic mode" discussions in the forum. Surprisingly it worked. However, I only get the transverse modes using this and not the lateral ones which were supposed to show up when sorted in ascending order. It doesn't make sense to use a shell solver for a 1D beam even though it worked for transverse eigen modes. Can anyone suggest the fix and right way to implement the 1D beam eigen analysis? I am pasting my solver setting based on the shell solver below. Thank you very much in advance.

Solver 1
Equation = "Shell equations"
Procedure = "ShellSolver" "ShellSolver"
Eigen Analysis = Logical True
Eigen System Values = Integer 5
Variable 1 = U 1
Variable 2 = U 2
Variable 3 = U 3
Variable 4 = Theta 1
Variable 5 = Theta 2
Variable 6 = Theta 3
Nonlinear System Max Iterations = 1
Nonlinear System Convergence Tolerance = 1e-7
Linear System Solver = "Iterative"
Linear System Preconditioning = Diagonal
Linear System Max Iterations = 1000
Linear System Componentwise Backward Error = True
Linear System Convergence Tolerance = 1e-7
Linear System Iterative Method = GCR
Linear System GCR Restart = 100
Linear System Abort Not Converged = False
Steady State Convergence Tolerance = 1e-09
End

[raback]

Hi

I just added the possibility to solve for eigenmodes (and a consistency test case):

https://github.com/ElmerCSC/elmerfem/co ... 49ba9ac4bf

Needs a fresh version of the code.

-Peter

[amarfayyad]

Hi Peter,
Sorry about the late reply. Thank you very much for this. I am new to Elmer hence the question. It seems Elmer GUI has been modified on 2023-09-05 from https://www.nic.funet.fi/pub/sci/physic ... s/?C=M;O=D . So, will this source code be reflected in it? If yes, if I update or re-install the new version of Elmer GUI and use the sif file provided will it work? or will I have to build the executable from the source code provided in https://www.elmerfem.org/blog/compile/? Thanks again.
-Amar

[Rich_B]

Hello,

Yes, changes in the source code will be included in each nightly build. Any changes should show up in one day, or maybe two days at the most.

Which OS are you using to run Elmer?

If Windows, download the latest installer from https://www.nic.funet.fi/pub/sci/physic ... n/windows/

If using a version of Linux, then downloading the latest ppa version should also get the latest nightly build.

Rich.

[amarfayyad]

Hi Rich,
Thank you very much. I am using Windows. To clarify, I will have to uninstall the current version and re-install the latest from https://www.nic.funet.fi/pub/sci/physic ... n/windows/ for the changes to take place. There is no way for the currently installed version to be updated (checking for updates and updating the software) feature yet for Elmer. I hope this is right. Thanks.
- Amar