Abstract
In this experimental work a scanning laser Doppler vibrometer is used to measure mode shapes and natural frequencies of beam bending vibrations above the critical frequency predicted by Timoshenko theory. Above the critical frequency the mode shapes are intricate, so to quantitative compare theoretical and experimental mode shapes, the modal assurance criterion (MAC) is applied. This reveals that the order of the modes is not as theory predicts, and that other plane modes can easily be misinterpreted as bending modes. This can lead to an incorrect comparison of natural frequencies. With the MAC tool it is found that the correlation between theoretical mode shapes and measured mode shapes is very high; It can be concluded that supercritical Timoshenko-predicted mode shapes agrees well with the experimentally observed modes, and the supercritical natural frequencies deviate from Timoshenko theory within five percent. Comparisons are made to other studies, and against a numerical 3D model.
| Original language | English |
|---|---|
| Article number | 114856 |
| Journal | Journal of Sound and Vibration |
| Volume | 459 |
| Number of pages | 14 |
| ISSN | 0022-460X |
| DOIs | |
| Publication status | Published - 2019 |
Keywords
- Critical frequency
- Modal assurance criterion
- Mode shapes
- Rotary inertia
- Scanning laser Doppler vibrometry
- Shear bending
- Timoshenko beam theory
- Timoshenko frequency pairs
Cite this
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Experimental testing of Timoshenko predictions of supercritical natural frequencies and mode shapes for free-free beams. / Brøns, Marie; Thomsen, Jon Juel.
In: Journal of Sound and Vibration, Vol. 459, 114856, 2019.Research output: Contribution to journal › Journal article › Research › peer-review
TY - JOUR
T1 - Experimental testing of Timoshenko predictions of supercritical natural frequencies and mode shapes for free-free beams
AU - Brøns, Marie
AU - Thomsen, Jon Juel
PY - 2019
Y1 - 2019
N2 - In this experimental work a scanning laser Doppler vibrometer is used to measure mode shapes and natural frequencies of beam bending vibrations above the critical frequency predicted by Timoshenko theory. Above the critical frequency the mode shapes are intricate, so to quantitative compare theoretical and experimental mode shapes, the modal assurance criterion (MAC) is applied. This reveals that the order of the modes is not as theory predicts, and that other plane modes can easily be misinterpreted as bending modes. This can lead to an incorrect comparison of natural frequencies. With the MAC tool it is found that the correlation between theoretical mode shapes and measured mode shapes is very high; It can be concluded that supercritical Timoshenko-predicted mode shapes agrees well with the experimentally observed modes, and the supercritical natural frequencies deviate from Timoshenko theory within five percent. Comparisons are made to other studies, and against a numerical 3D model.
AB - In this experimental work a scanning laser Doppler vibrometer is used to measure mode shapes and natural frequencies of beam bending vibrations above the critical frequency predicted by Timoshenko theory. Above the critical frequency the mode shapes are intricate, so to quantitative compare theoretical and experimental mode shapes, the modal assurance criterion (MAC) is applied. This reveals that the order of the modes is not as theory predicts, and that other plane modes can easily be misinterpreted as bending modes. This can lead to an incorrect comparison of natural frequencies. With the MAC tool it is found that the correlation between theoretical mode shapes and measured mode shapes is very high; It can be concluded that supercritical Timoshenko-predicted mode shapes agrees well with the experimentally observed modes, and the supercritical natural frequencies deviate from Timoshenko theory within five percent. Comparisons are made to other studies, and against a numerical 3D model.
KW - Critical frequency
KW - Modal assurance criterion
KW - Mode shapes
KW - Rotary inertia
KW - Scanning laser Doppler vibrometry
KW - Shear bending
KW - Timoshenko beam theory
KW - Timoshenko frequency pairs
U2 - 10.1016/j.jsv.2019.114856
DO - 10.1016/j.jsv.2019.114856
M3 - Journal article
VL - 459
JO - Journal of Sound and Vibration
JF - Journal of Sound and Vibration
SN - 0022-460X
M1 - 114856
ER -