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TECHNICAL PAPERS

Investigation of Curved Polymeric Piezoelectric Active Diaphragms

[+] Author and Article Information
Kelly C. Bailo, Diann E. Brei, Karl Grosh

Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, Ann Arbor, MI 48109-2125

J. Vib. Acoust 125(2), 145-154 (Apr 01, 2003) (10 pages) doi:10.1115/1.1547461 History: Received October 01, 2000; Revised September 01, 2002; Online April 01, 2003
Copyright © 2003 by ASME
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References

Figures

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Acoustic PVdF transducer configuration: Defined by radius (R), width (b), subtended angle (θs), and thickness (t), which is broken down into electrode layer thickness (te-nominal 6.5 μm), piezoelectric layer thickness (tp-nominal 28 or 52 μm) and bonding layer thickness (tb-nominal 40 to 60 μm). (a) Bending lay-up: Layers strain in opposing directions above and below the neutral axis. (b) Extension lay-up: All layers are configured such that as a voltage is applied, they all strain in one circumferential direction.
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Numerical model meshes (typical): Example numerical model meshes for (a) ABAQUS dynamic model. Defined by radius (R) and thickness (t) with element aspect ratios kept near 1:1 in high stress regions which occur near the fixed end constraints. (b) COMET acoustic model. Defined by radius (R), width (b), and subtended angle (θs), consisting of approximately 100 two-dimensional elements along the arc length and six through the width.
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Prototypes set up for experimentation: Constant curvature prototypes placed in aluminum clamps ready for dynamic and acoustic experimental testing.
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Acoustic experimental set-up: (a) Schematic. General acoustic experimental equipment set up, showing the transducer powered by an HP 35670A dynamic signal analyzer through a Piezosystems Model ESA-203 voltage amplifier with data acquisition by a Realistic brand sound level meter (microphone). (b) Photo. Near field acoustic experimental set-up showing a microphone set up at a distance of 10 cm from the vibrating surface of the transducer.
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Typical dynamic displacement correlation: Experimental versus numerical results for a prototype configured with four layers of 28 micron PVdF, radius=25 mm,width=20 mm, subtended angle=90 deg,thickness=394 μm and 75 Volts applied.
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Typical acoustic frequency correlation: Experimental versus numerical results for a prototype configured with four layers of 28 micron PVdF with a vibrating surface area of 68 mm wide by 96 mm long and a subtended angle of 25 deg tested at 100 volts, resulting in a peak output of 103 dB at 1730 Hz. The results correlation shows acoustic sound pressure variations ranged from 1 to 7 dB with an average backbone variation of less than 3 dB.
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Thickness study: Results for varying thickness single-layer prototypes with radius=45 mm,width=20 mm, subtended angle=90 deg and applied electric field=30 V/μm. (a) Numeric simulation results. Mode number is indicated above each resonance peak. (b) Analytic simulation results. 2D prediction of total acoustic response.
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Analytic prediction: 2D analytic prediction for single-layer prototype with thickness=1 mm,radius=45 mm,width=20 mm, subtended angle=90 deg and applied electric field=30 V/μm. Total solution is compared to particular solution.
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Numerical radius study: Results for a single-layer prototype with thickness=1 mm,width=20 mm, subtended angle=90 deg and applied electric field=30 V/μm. Mode number is indicated above each resonance peak.
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Numerical subtended angle study: Results for a single-layer (28 μm PVdF) prototype with an arc length=100 mm,width=20 mm and applied electric field=30 V/μm. (a) Acoustic frequency response. Prototype configured with subtended angles, θs=5deg, 15 deg, 90 deg illustrating that the acoustic response for the transducer configured at 15 deg is higher than that of the other configurations in the frequency range above 750 Hz. (b) Optimal subtended angle at 1250 Hz. Results illustrate that there exists an optimal subtended angle occurring near 15 deg.
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Analytic subtended angle study: Results for a single-layer (28 μm PVdF) prototype with an arc length=100 mm,width=20 mm and applied electric field=30 V/μm, configured with subtended angles, θs=5 deg and 15 deg.
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Experimental subtended angle study: Results measured in the far-field at 1.2 meters for a four-layer (28 μm PVdF) prototype with an arc length=68 mm,width=96 mm and 200 volts applied. (a) Acoustic frequency response. Prototype configured with subtended angles, θs=10 deg, 30 deg, 45 deg. (b) Optimal subtended angle at 1100 Hz and 1920 Hz. Results illustrate that there exists an optimal subtended angle occurring between 15 deg and 20 deg in this frequency range.
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Experimental subtended angle study at 1100 Hz: Results measured in the far-field at 1.2 meters for two four-layer (28 μm PVdF) prototypes with 200 volts applied. Configuration 1 consists of an arc length=68 mm and width=96 mm while configuration 2 consists of an arc length=96 mm and width=68 mm.
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Voltage variation with respect to 4 volt baseline linear response in near field at 10 cm: Four-layer (28 μm PVdF) prototype with an arc length=96 mm,width=67 mm and 200 volts applied. Straight lines indicate a theoretical extrapolation of the expected linear increase in sound levels with increased power w.r.t. the 4 volt baseline, while the jagged line shows the measured response. At low voltages the device behaves relatively linearly, while at higher frequencies the response drops off at voltages as low as 50 volts, indicating nonlinear behavior in the device.

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