Henrik Sönnerlind
COMSOL Employee

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Posted:
2 years ago
28 set 2022, 14:30 GMT-4

You may get some help by looking at the tutorial model bracket_eigenfrequency in Application Libraries.

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Henrik Sönnerlind

COMSOL

You may get some help by looking at the tutorial model bracket_eigenfrequency in Application Libraries.

Acculution ApS
Certified Consultant
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Posted:
2 years ago
28 set 2022, 14:47 GMT-4

Pretty sure loads are omitted by the solver when you run an eigenvalue problem. As it well should be, since you don't have sources in a eigenvalue problem.

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René Christensen, PhD

Acculution ApS

www.acculution.com
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Pretty sure loads are omitted by the solver when you run an eigenvalue problem. As it well should be, since you don't have sources in a eigenvalue problem.

Henrik Sönnerlind
COMSOL Employee

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Posted:
2 years ago
28 set 2022, 16:02 GMT-4

René,

I think we are talking about a prestressed eigenfrequnecy analysis here since load dependency is to be investigated (that is, the second study in the tutorial I suggested). But you are right in that loads as such are ignored in an eigenfrequency analysis as long as they are not 'follower loads' like pressure.

-------------------

Henrik Sönnerlind

COMSOL

René,
I think we are talking about a prestressed eigenfrequnecy analysis here since load dependency is to be investigated (that is, the second study in the tutorial I suggested). But you are right in that loads as such are ignored in an eigenfrequency analysis as long as they are not 'follower loads' like pressure.

Acculution ApS
Certified Consultant
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Posted:
2 years ago
3 ott 2022, 05:25 GMT-4

Ah yes Henrik, I think you are right. Thought it was a time-varying load of sorts.

-------------------

René Christensen, PhD

Acculution ApS

www.acculution.com
info@acculution.com

Ah yes Henrik, I think you are right. Thought it was a time-varying load of sorts.

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Posted:
2 years ago
13 ott 2022, 02:22 GMT-4

Updated:
2 years ago
13 ott 2022, 08:05 GMT-4

Thank you for your replies. It was truly helpful. I have one more question.
I added a block at the free end of the cantilever, assigned a blank material with poisson ratio, young modulus and density. Since density (rho) is mass divided by the volume, I was able to give different mass to calculate the rho value, which in turn gave different value of eigen frequency, without making use of any body/boundary load. In the 'eigen frequency, prestressed study' , the load is in terms of force, but I want calculate the change in terms of mass. If I want to measure change in the eigen frequency with different mass, is this the right way to do it? Without making use of any body load. (Since different mass gives differnt values of rho which causes a change in the eigen frequency) The same change in eigen value by changing rho value was also obtained for the 'eigen frequency' where load is not applied. I am confused on how to go about it. Please share your valuable advice/suggestions. Thank you.

Thank you for your replies. It was truly helpful. I have one more question.
I added a block at the free end of the cantilever, assigned a blank material with poisson ratio, young modulus and density. Since density (rho) is mass divided by the volume, I was able to give different mass to calculate the rho value, which in turn gave different value of eigen frequency, without making use of any body/boundary load. In the 'eigen frequency, prestressed study' , the load is in terms of force, but I want calculate the change in terms of mass. If I want to measure change in the eigen frequency with different mass, is this the right way to do it? Without making use of any body load. (Since different mass gives differnt values of rho which causes a change in the eigen frequency) The same change in eigen value by changing rho value was also obtained for the 'eigen frequency' where load is not applied. I am confused on how to go about it. Please share your valuable advice/suggestions. Thank you.