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Eigenfrequency shift due to thermal expansion
Posted 01.07.2015, 12:34 GMT-4 Heat Transfer & Phase Change, Studies & Solvers, Structural Mechanics Version 4.3 1 Reply
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Hi,
I'm new to Comsol and the Comsol I'm using is 4.3. I would like to study the eigenfrequency shift of a solid cylinder over the time when an infrared laser is heating one of its surface. The heating will cause thermal stress and expansion change inside the material thus changing the eigenfrequency. So I use "Joule Heating and Thermal Expansion" physics. First, I run a time dependent study and then run a new study of eigenfrequency to find resonant frequencies around 15,000 Hz. I want to use the result of the time-dependent study as the initial parameters of the eigenfrequency study. So in "Values of variables not solved for" of eigenfrequency study, I choose the time dependent solution at a certain time. However, no matter which time I choose, from the "Mode Shape" in the Results the Comsol always give me the same eigenfrequencies. I also tried to use "Initial Values of Variables Solved for" but it doesn't work either. Can anyone suggest which points I missed in order to do it properly? I have attached my file but I deleted the solver configurations in order to save space (I used the default solvers).
I'm new to Comsol and the Comsol I'm using is 4.3. I would like to study the eigenfrequency shift of a solid cylinder over the time when an infrared laser is heating one of its surface. The heating will cause thermal stress and expansion change inside the material thus changing the eigenfrequency. So I use "Joule Heating and Thermal Expansion" physics. First, I run a time dependent study and then run a new study of eigenfrequency to find resonant frequencies around 15,000 Hz. I want to use the result of the time-dependent study as the initial parameters of the eigenfrequency study. So in "Values of variables not solved for" of eigenfrequency study, I choose the time dependent solution at a certain time. However, no matter which time I choose, from the "Mode Shape" in the Results the Comsol always give me the same eigenfrequencies. I also tried to use "Initial Values of Variables Solved for" but it doesn't work either. Can anyone suggest which points I missed in order to do it properly? I have attached my file but I deleted the solver configurations in order to save space (I used the default solvers).
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1 Reply Last Post 02.07.2015, 08:38 GMT-4
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Posted:
9 years ago
Hi,
There are different effects which may cause a change of eigenfrequnecies with temperature:
a) Changes in material data with temperature
b) Changes in geometry (usually small)
c) Stress stiffening caused by thermal stresses
Of course, it can also be a combination.
There are different things you need to consider here, so first you need to state which effects you are looking for. There are several discussions about this in the forum, see for example
www.comsol.com/community/forums/general/thread/47241
www.comsol.com/community/forums/general/thread/34427
Regards,
Henrik
There are different effects which may cause a change of eigenfrequnecies with temperature:
a) Changes in material data with temperature
b) Changes in geometry (usually small)
c) Stress stiffening caused by thermal stresses
Of course, it can also be a combination.
There are different things you need to consider here, so first you need to state which effects you are looking for. There are several discussions about this in the forum, see for example
www.comsol.com/community/forums/general/thread/47241
www.comsol.com/community/forums/general/thread/34427
Regards,
Henrik