Eigen value analysis

Numerical methods and mathematical models of Elmer
Sayan
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Eigen value analysis

Post by Sayan »

Hii Team,
I have modelled one beam with 3 blocks together and analysed to extract natural frequency values. But the results are not correct. Can anyone please help me to solve this issue??
Attachments
crackbeam.msh
(117.62 KiB) Downloaded 139 times
crackbeam.geo
(51 Bytes) Downloaded 142 times
case.sif
(1.63 KiB) Downloaded 149 times
kevinarden
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Re: Eigen value analysis

Post by kevinarden »

The model has coincident nodes and therefor the three blocks are separate independent bodies. Was this the intent?
Sayan
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Re: Eigen value analysis

Post by Sayan »

The model will have 3 bodies with different properties for further analysis. But to start with I wanted to find out the natural frequency of the system as a whole with same property.
kevinarden
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Re: Eigen value analysis

Post by kevinarden »

There is a difference between three independent bodies not attached to each other and three bodies attached but with different properties. Currently you have three independent bodies not attached to each other.
Sayan
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Re: Eigen value analysis

Post by Sayan »

It should be an attached body in my case..I have also used common edge of different parts to join them node to node using FreeCad... In this way previously I got an attached body with modification of geo file where mesh has been merged at co-incident points.. For this case if it's showing different bodies which are not connected, how can I join them to get a connected body?
kevinarden
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Re: Eigen value analysis

Post by kevinarden »

One way is to use ElmerGrid to convert the mesh and merge the coincident nodes.

ElmerGrid 14 2 cracked.msh -merge 1.e-8

Another whay is to use the coherence command in gmsh to merge the coincident points prior to exporting he mesh,
Sayan
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Re: Eigen value analysis

Post by Sayan »

Hiii,
Thank you... But if you look into my .geo file you can see I have used coherence mesh command before exporting to Elmer..You suggested me this earlier for another model..That time with this modification I got good result...But this time it's not working in this model..Don't know why..
Rich_B
Posts: 421
Joined: 24 Aug 2009, 20:18

Re: Eigen value analysis

Post by Rich_B »

Hi,

Looking at the contents of the .geo file, it looks questionable:
Merge "crackbeam.msh";
//+
//+
Coherence Mesh;
Try adding the Coherence command before generating the mesh that gets stored in 'crackbeam.msh'. Adding the Coherence command after the meshing operation has finished and has been written to file, may possibly be the issue.

Let us know what you find out.

Rich.
Sayan
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Re: Eigen value analysis

Post by Sayan »

Hii,
After generating .geo file while using Gmsh and before doing meshing I edited the .geo file and inserted the coherence command,..Then I create meshing and save and then export.. Following this I have got no improvement.. I am attaching my new .geo file with case.sif here..
Attachments
crackbeamf.msh
(205.53 KiB) Downloaded 138 times
crackbeamf.geo
(202 Bytes) Downloaded 133 times
crackbeamf.brep
(32.02 KiB) Downloaded 133 times
kevinarden
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Re: Eigen value analysis

Post by kevinarden »

It still has coincident nodes. I am able to merge them with ElmerGrid.
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