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Stress/vibration analysis
Posted 27 apr 2012, 02:26 GMT-4 MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Structural Mechanics 3 Replies
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Hey,
I want to do a stress analysis on a structure exposed to vibrations in the range of 100-2.5k Hz
I’ve made an attempt by using the Frequency-Domain Modal study in the Solid Mechanics interface.
I’ve tried using different frequency sweeps but don’t get any results (0 displacement for all frequencies), although I’ve managed to run the Egienfrecuency study successfully.
I’ve attached my model in this mail. I would be very grateful if someone could give me some feedback on my model.
/Ulrika
I want to do a stress analysis on a structure exposed to vibrations in the range of 100-2.5k Hz
I’ve made an attempt by using the Frequency-Domain Modal study in the Solid Mechanics interface.
I’ve tried using different frequency sweeps but don’t get any results (0 displacement for all frequencies), although I’ve managed to run the Egienfrecuency study successfully.
I’ve attached my model in this mail. I would be very grateful if someone could give me some feedback on my model.
/Ulrika
Attachments:
3 Replies Last Post 20 nov 2014, 04:51 GMT-5
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Posted:
1 decade ago
Hi
A frequency domain analysis applies a Force load (that you have forgotten to define) as an amplitude mutliplied by a constant sinus type excitation at a frequency range you define.
The second effect is that you have resonaces around 25 kHz and you are plotting the respons around 100 Hz, you will see nothing so far away from your resonance.
I would propose:
1) perform a eigenfrequency to get the modes
2) start with frequency domain (then later go to frequency - modal) for a frequency range ot +/- 5% around your first resonance
3) define a load, i.e. a body gravity load Fy=g_const*solid.rho
then run
Another point to consider: damping, without any damping the resoance are so sharp that often COMSOL either skip then or fail to pass the resonance
To get back to your frequency-domain modal :
Do not forget: !!!!
you need to right click the body or boundary load and add a "Harmonic perturbation" tick this will add the "tilda" on the icon and your load will now be correctly set up .
--
Good luck
Ivar
A frequency domain analysis applies a Force load (that you have forgotten to define) as an amplitude mutliplied by a constant sinus type excitation at a frequency range you define.
The second effect is that you have resonaces around 25 kHz and you are plotting the respons around 100 Hz, you will see nothing so far away from your resonance.
I would propose:
1) perform a eigenfrequency to get the modes
2) start with frequency domain (then later go to frequency - modal) for a frequency range ot +/- 5% around your first resonance
3) define a load, i.e. a body gravity load Fy=g_const*solid.rho
then run
Another point to consider: damping, without any damping the resoance are so sharp that often COMSOL either skip then or fail to pass the resonance
To get back to your frequency-domain modal :
Do not forget: !!!!
you need to right click the body or boundary load and add a "Harmonic perturbation" tick this will add the "tilda" on the icon and your load will now be correctly set up .
--
Good luck
Ivar
Attachments:
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Posted:
1 decade ago
Thank you very much Ivar!
I think I get it now =)
I think I get it now =)
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Posted:
1 decade ago
Hi
Could you please answer the following
1. Do we have to have booth boundary as well as body loads as contained in your file?
2. I want to apply a load of 250 uN , do I have to convert it into G force?
Thanks for your time
Regards
Anurekha
Could you please answer the following
1. Do we have to have booth boundary as well as body loads as contained in your file?
2. I want to apply a load of 250 uN , do I have to convert it into G force?
Thanks for your time
Regards
Anurekha
Hi
A frequency domain analysis applies a Force load (that you have forgotten to define) as an amplitude mutliplied by a constant sinus type excitation at a frequency range you define.
The second effect is that you have resonaces around 25 kHz and you are plotting the respons around 100 Hz, you will see nothing so far away from your resonance.
I would propose:
1) perform a eigenfrequency to get the modes
2) start with frequency domain (then later go to frequency - modal) for a frequency range ot +/- 5% around your first resonance
3) define a load, i.e. a body gravity load Fy=g_const*solid.rho
then run
Another point to consider: damping, without any damping the resoance are so sharp that often COMSOL either skip then or fail to pass the resonance
To get back to your frequency-domain modal :
Do not forget: !!!!
you need to right click the body or boundary load and add a "Harmonic perturbation" tick this will add the "tilda" on the icon and your load will now be correctly set up .
--
Good luck
Ivar