Comsol Conference September 24 th 26 th 2019 Cambridge Author Sam Jackson Introduction What is an OpenType Flexural Ultrasonic Transducers Crosssection from Murata Introduction ID: 780109
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Slide1
Modelling of Open-Type Flexural Ultrasonic Transducers
Comsol
Conference
September 24
th
- 26
th 2019CambridgeAuthor: Sam Jackson
Slide2Introduction
What is an Open-Type
Flexural Ultrasonic
Transducers?
Cross-section from Murata
Slide3Introduction
Scope of this work
Measure response characteristics of a single transducer type (electro-mechanical and acoustic).
Model transducer operation using
Comsol
Multiphysics
Use simulation and experiment to gain a deeper understanding of the operation of open-type flexural ultrasonic transducers.
Slide4System Breakdown
Assumptions Made
Components perfectly bonded and separable.
Disk material: Brass, Horn material: Aluminium.
Piezo material: PZT-5A (best fit to data).
Dimensions measured with a
micrometer
and a 3-axis vision machine.
Profile of horn approximated as line of best fit through measured points.
Slide5Model Setup
Multiphysics
modelling combining piezo, mechanical and acoustic domains.
Steady state response at discrete
frequencies.
Mechanical damping term added to piezo element to best fit rated Q-factor.
Rayleigh damping added to horn to represent losses due to bending.
Disk bender
undamped
.
Slide6System Response
What is measured
Electromechanical (impedance), mechanical (component velocity, and acoustic response).
Model Shapes
Three excitation voltages, 1
V
rms
(linear regime), 10
V
rms
(rated operation) and 20
V
rms
(high power operation).
How it was measured
Sweep response between 30 kHz and 60 kHz.
Voltage probe and current clamp to obtain impedance curve.
Polytec
PSV-400 laser
vibrometer
to measure velocity.
GRAS 46BE free field microphone to measure acoustic response.
Slide7System Response - Impedance
Simulated (
dashed line
) and
experimentally measured
(solid
line) electrical
impedance
of the
transducer disk
an piezo. Excitation
applitude
of 1
Vrms
(Blue),
10
Vrms
(Red) and
20
Vrms
(Yellow
).
Simulated (
dashed line
) and
experimentally measured
(solid
line) electrical
impedance
of the full transducer. Excitation
applitude
of 1
Vrms
(Blue),
10
Vrms
(Red) and
20
Vrms
(Yellow
).
Impedance – gives an insight into the response and operation of the piezo
Slide8System Response – Mechanical
Single disk/piezo mode, two transducer modes.
Two coupled single DOF systems.
Combination of symmetric and asymmetric modes
Slide9System Response – Mechanical
Horn Mode (3,1)
Horn Mode (0,1)
Out of Phase
Horn Mode (3,1)
In Phase
Horn Mode (4,1)
33 kHz
40 kHz
51 kHz
55 kHz
28 kHz
40 kHz
49 kHz
47 kHz
Estimated Horn Shape
Slide10System Response – Mechanical
Horn Mode (3,1)
Horn Mode (0,1)
Out of Phase
Horn Mode (3,1)
In Phase
Horn Mode (4,1)
33 kHz
40 kHz
51 kHz
55 kHz
32
kHz
38
kHz
48
kHz
54
kHz
Scanned
Horn Shape
Slide11System Response – Mechanical
Measured velocity response amplitude (top) and relative phase (bottom) across the diameter of the horn at the first (blue) and second (red) resonant modes.
Simulated (dashed line) and experimentally measured (solid line) frequency response (top) and phase (bottom) of the full
tranducer
at the horn
center
(blue), horn edge (red) and disk edge (yellow). Excitation amplitude of 1
Vrms
.
Slide12System Response - Acoustic
Acoustic Response – What the transducer actually generates
Simulated (dashed line) and experimentally measured (solid line) acoustic response of the transducer at a distance of 50 mm. Excitation
applitude
of 1
Vrms
(Blue), 10
Vrms
(Red) and 20
Vrms
(Yellow).
Normalised simulated (dashed line) and experimentally measured (solid line) acoustic response of the transducer at a distance of 50 mm. Excitation
applitude
of 1
Vrms
(Blue), 10
Vrms
(Red) and 20
Vrms
(Yellow). Note that simulated impedance curves for different voltage levels are indistinguishable.
Slide13Conclusion
Strongly coupled 2 DOF system (disk/piezo and horn)
Nonlinearity and drop in Q-factor driven by piezo.
Horn acts as a mechanical amplifier, adds damping to the system.
Two symmetric transducer modes, second mechanically dominant, first acoustically dominant.
Mis
-alignment between piezo resonance (minimum impedance) and system mechanical resonance causes significant drop in acoustic efficiency and Q-factor.
Key Outcomes
Slide14Questions
Thank You
Any Questions?