TPC- Measurement Techniques
Damien Maillard, Muhammad FaizanProf. Guillermo Villanueva
Dynamical Models
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Amplitude/Phase
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Statique
Phase = 0,la masse suit la force
Inertie
Phase = -Pi,la masse ne suit plus la
force
Résonnance d’amplitude
Phase = – Pi/2
Amplitude Max
Real/Imaginary
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Résonance, ω = 5
Amplitude max
Amplitude max
Frequency Response Function (FRF)
● FRF is a ratio of output (vibrations of a mechanical structure) over input (excitation force)
● Excite structure at different points and get FRF’s to plot the mode shape
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( ) ∑= −+
==n
k kkkk
ks
kr
s
rrs jηm
ββjFjXjh
122 ) 2()(
)(ωωωωω
ωω
Objectives of the Tp
● Assembling the measurement setup (wing, hammer, accelerometer).
● Understand different settings (sampling freq, actuation time, triggering etc) of the measurement software (LabView).
● Measurement of a frequency response function of a structure.
● Study and understand the effect of mass addition to the structure.
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Procedure
● Properly mount the wing with the clamping system
● Use hammer with appropriate head to excite the wing
● Observe the time domain and frequency responses of the hammer and accelerometer
● Use FRF analysis to measure different resonance frequencies
● Attach magnets to increase the weight of the wing and again observe resonance frequencies
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Excitation System
● Hammer Headso Teflon, Metal, rubber
● Selection of hammer heado Time domain response (high no. of points on the
pulse)o Frequency domain response (flat)
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Time response Frequency response
Accelerometer
● Piezoelectric accelerometero Max displacement => Maximum force => maximum acceleration
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M
F=M a
k
Pièzo
System Block Diagram
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Données de Sortie et Affichage
Traitement de Signal
a(t)
f(t)Echantillonnage
Filtrepasse bas
Filtrepasse bas
Echantilloneur
Echantilloneur
FenètreTemporelle
FenètreTemporelle
FFT
FFT
acmplx(ω)
fcmplx(ω)
FRFimoyenne
1/n Σ (FRFi)
- Fréq. Echantillonnage- Nbre d'échantillons
Type et paramètres desfenètres temporelles - Méthode et paramètres
de Moyennage- Paramètres d'affichage
Préa
mpl
i
Niveauxd'entrée
Modal Shapes (Example)
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Tp Documentation
● All the necessary documents for the practical work can be found on the web at:http://wiki.epfl.ch/me301-tdm/tpc
● The report must be sent at the latest 2 weeks after the TP by email to [email protected] or [email protected]
● Do not send the scanned version of the report. Use computer to type it
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TPC- Measurement Techniques Dynamical ModelsAmplitude/PhaseReal/Imaginary Frequency Response Function (FRF)Objectives of the TpProcedureExcitation SystemAccelerometer System Block DiagramModal Shapes (Example)Tp Documentation
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