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Capacitive Micro machined Ultrasonic
Transducers arrays (CMUTs) for
Structural Health Monitoring (SHM).
Journée nationale contrôle sante et monitoring des structures
March 12, 2020, Paris, France
Presented by : Redha BOUBENIA
In collaboration with: Gilles BOURBON
Patrice LE MOAL
Vincent PLACET
Éric JOSEPH
Emmanuel RAMASSO
NuclearOiler…Aerospace Medical
The real interest of the industrial sector for ultrasonic non-destructive testing
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
2
❖ Maintenance is performed on immobilized devices
❖ Currently more than 25% of lifecycle costs are spent on inspection and reparation
❖ We develop acoustic instrumentation and technique for Structural Health Monitoring (SHM)
• Detection of damage on real-time
• Help for simulation validation
• Collection of data
• Predictive analysis
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
3
Frequency range0.1 – 1 MHz
Acoustic Emission Source
❖ Size: little intrusive into the material
❖ High bandwidth
Electrical connector Electrical conductor
BackingActive element (piezoelectric)
Front face (adaptation face)
Piezoelectric sensor
polysilicon membrane
nitride layer
ground electrode
feed electrode
anchor postsilicon substrate
gap
A-A
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
4
❖ Size: little intrusive into the material
❖ High bandwidth
Electrical connector Electrical conductor
BackingActive element (piezoelectric)
Front face (adaptation face)
Piezoelectric sensor Capacitive sensor
polysilicon membrane
nitride layer
ground electrode
feed electrode
anchor postsilicon substrate
gap
A-A
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
5
❖ Frequency : 𝑓𝑟 = Τ𝑣2𝑒
❖ Size: 10 mm diameter X 12 mm height
Electrical connector Electrical conductor
BackingActive element (piezoelectric)
Front face (adaptation face)
Piezoelectric sensor Capacitive sensor
polysilicon membrane
nitride layer
ground electrode
feed electrode
anchor postsilicon substrate
gap
A-A
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
❖ Frequency :𝑓𝑟 =λ2
2𝜋𝑅2ℎ
𝐸
12𝜌(1−ν2)
❖ Size: 16 mm diameter X 1.6 mm height
6
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
polysilicon membrane
nitride layer
ground electrode
feed electrode
anchor postsilicon substrate
gap
A-A❖ Capacitive Micro machined Ultrasonic Transducer (CMUT):
▪ 2.5 mm X 2.5 mm chip
▪ 40 elementary cells
▪ PCB 12 mm diameter for electrical contact
▪ Wire bonded
▪ Encapsulated on 16 mm diameter
7
polysilicon membrane
nitride layer
ground electrode
feed electrode
anchor postsilicon substrate
gap
A-A
❖ Validation of ability of CMUT to detect Acoustic Emission (AE)
❖ Validation of the ability to have an electrical measurement
❖ Improvement and development of the electrical measuring system
❖ Identification of the best configuration in the choice of electrical parameters
❖ Improvement of the signal noise ratio (S/N) : hard and soft
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
8
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
9
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
❖ Bias voltage is adjusted between 0V to collapse voltage
❖ We applied VAC=0.5V peak-to peak with a synthesizer function generator (Helwett Packard 3325 B
❖ We measured the maximum amplitude of CMUT-R100 with laser Polytec vibrometer
❖ Collapse voltage at 85 V
❖ We applied 80% of collapse voltage
❖ Bandwidth frequency between 300 KHz to 500 KHz
10
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
11
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
Aluminium
CMUTTransducteur µ80/E
µ80/R
12
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
13
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
14
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Introduction Characterisation techniques Experimental results Conclusion
15
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
Micro-80/E
CMUT-R100
Micro-80/R
Flax / epoxy
specimen
Instron Electropuls E10000 machine
❖ MTS Criterion machine equipped with 100 kN
❖ Load sensor control 0,1 mm/s axial
❖ 3 sensors are placed on flax /epoxy plate
❖ Streaming data of AE signal was recorded during 50 seconds
16
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
❖ CMUT-R100 depicts an important AE activity compared with Micro-80/R
❖ At the end of tensile test, three transducers have the same amplitude of AE activity (80 dB)
17
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
❖ CMUT-R100 shows an important AE frequency activity
❖ The shape response of the three transducers is similar
❖ At the end of tensile test, the frequency response of CMUT-R100 is comparable to µ80 E and R
18
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
❖ Improvement of the detected signal
▪ Amplitude CMUT-V1: 7 mV
▪ Amplitude CMUT-R100: 30 mV
❖ Miniaturisation of the capacitive transducer
▪ Volume CMUT-V1: 2304 mm3
▪ Volume CMUT-R100: 322 mm3
19
▪ Electrical characterisation
▪ Acoustical Characterisation▪ Tensile test on flat /epoxy
▪ Signal amplitude comparison
▪ Signal frequency comparison
▪ Conclusion
▪ Perspective
Introduction Characterisation techniques Experimental results Conclusion
▪ Context
▪ Capacitive and piezoelectric sensors
▪ Problematic
❖ Improvement of signal noise ratio
❖ Increase number of elementary cell
❖ Acoustical mismatching
❖ Line impedance mismatching
❖ Study influence of diameter of electrode
❖ The goal is to reach S/N of CMUT-R100 to S/N of µ80/R
20
Thank you for your attention
Journée nationale contrôle sante et monitoring des structures
March 12, 2020, Paris, France
Presented by : Redha BOUBENIA
In collaboration with: Gilles BOURBON
Patrice LE MOAL
Vincent PLACET
Éric JOSEPH
Emmanuel RAMASSO
22Travaux 2019-2020 : Etude de la réponse acoustique d’une
membrane en fonction du couplage
Le signal reçu peut être divisé par deux dans certain cas
VDC=65V
23Travaux 2019-2020 : Etude de la réponse acoustique d’une
membrane en fonction du couplage
Le signal reçu peut être divisé par deux dans certain cas
VDC=65V
24Travaux 2018-2019 : Premier essai sur éprouvette
(Aluminium) 1V
25Travaux 2018-2019 : Premier essai sur éprouvette
(Aluminium) 1V
26Travaux 2019-2020 : Premier essai sur éprouvette
(Aluminium) 200mV
27Travaux 2019-2020 : Premier essai sur éprouvette
(Aluminium) 200mV (après filtre Matlab)
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