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Truss interface - excitation

Posted 13 mars 2014, 08:06 UTC−4 Acoustics & Vibrations, Structural Mechanics Version 4.1, Version 4.2, Version 4.2a, Version 4.3, Version 4.3a, Version 4.3b, Version 4.4 2 Replies

Nicolas Tsagarakis
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Hello,

Since I read that the truss interface can only sustain axial forces, does anyone know if I could do a frequency domain study and excite the system by a transverse force?

thanks,
Nicolas T.
2 Replies Last Post 18 mars 2014, 17:00 UTC−4
Nicolas Tsagarakis
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Posted: 1 decade ago 18 mars 2014, 16:57 UTC−4
Hello again,
I made a model in order to experiment on that.

Firstly, I began by taking the Comsol model of the "vibrating string", and modifying it in the ways I wanted.

I left the tension as it was, but I tried to determine, at start, the free-free vibration modes. I thought a way of making that was to set the prescribed displacement at x direction to be zero, but move freely in the y direction.
I can see by the mode shapes and frequencies that this worked well.

Secondly, I added a frequency domain study, and excited an arbitrary point by a point load.
Next, through "derived values" I calculated and plotted the square of the absolute value of the mean displacement.
I can see two resonant frequencies, at ~440 and 880Hz as expected (the sweep was 350 to 1000 by a step of 2)

I have some problems and a lot of questions, but the main issue is the one I mentioned in the above post.

How can this happen, to excite a string in truss element in the transverse direction, when the truss can sustain only axial forces?

I would appreciate it if someone could check my model for any other mistakes and suggestions in general.

Thanks for your time,
Nicolas T.
Hello again, I made a model in order to experiment on that. Firstly, I began by taking the Comsol model of the "vibrating string", and modifying it in the ways I wanted. I left the tension as it was, but I tried to determine, at start, the free-free vibration modes. I thought a way of making that was to set the prescribed displacement at x direction to be zero, but move freely in the y direction. I can see by the mode shapes and frequencies that this worked well. Secondly, I added a frequency domain study, and excited an arbitrary point by a point load. Next, through "derived values" I calculated and plotted the square of the absolute value of the mean displacement. I can see two resonant frequencies, at ~440 and 880Hz as expected (the sweep was 350 to 1000 by a step of 2) I have some problems and a lot of questions, but the main issue is the one I mentioned in the above post. How can this happen, to excite a string in truss element in the transverse direction, when the truss can sustain only axial forces? I would appreciate it if someone could check my model for any other mistakes and suggestions in general. Thanks for your time, Nicolas T.
Nicolas Tsagarakis
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Posted: 1 decade ago 18 mars 2014, 17:00 UTC−4
P.S. I attach my model.
P.S. I attach my model.

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