• Journal of radiological science and technology
• /
• v.23 no.2
• /
• pp.33-37
• /
• 2000

The authors fabricated ultrasonic transducer with PVDF[poly(vinylidene fluoride)] piezoelectric polymer film. When impulse waves were applied to the PVDF ultrasonic transducer, the dependence of the response properties on the backing material with copper was investigated through not only theoretical calculations using Mason's equivalent circuit but also experimental measurements. The experimental pulse response properties agree with those of the theoretical calculations and the pulses were shorter than those for a PZT transducer. If such short-pulse properties are used in an medical ultrasonic image diagnosis apparatus, the resolution of the apparatus will be improved. When the insertion loss was calculated theoretically to the PVDF ultrasonic transducer, the frequency characteristics of its showed wideband frequency.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.1
• /
• pp.1-8
• /
• 2002

The high frequency ultrasonic transducers using polyvinyliden fluoride(PVDF) and polyvinylidene fluoride trifluorethyylene(P(VDF-TrFE)) were developed. The characteristics of fabricated high frequency ultrasonic transducer such as beam diameter, high frequency ultrasonic detection field and amplitude of the first pulse echo signal from the test target in the water were analyzed. The high frequency ultrasonic detection field was affected by the length of coaxial cable between high frequency transducer and ultrasonic pulser/receiver. As the size of the test target increased, the high frequency detection field decreased and the amplitude of a reflection signal increased. The peak amplitude of the first pulse echo signal of P(VDF-TrFE) transducer was higher than that of PVDF transducer. The high frequency ultrasonic detection field of PVDF transducer was wider than that of P(VDF-TrFE) transducer. With C-scan testing, the developed high frequency ultrasonic transducer could detect the 30 to $100{\mu}m$ of hydrogen induced crack of steel specimen by C-scan testing.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.6
• /
• pp.519-524
• /
• 2009

This work presents a simple technique to determine the Poisson's ratio of homogeneous solid material using a pair of low cost PVDF ultrasonic transducers. It is based on transducer's property of generating longitudinal and transversal waves depending on the excitation frequency. Mechanical tests were conducted to validate the proposed method, resulting in a good agreement between ultrasonic and mechanical techniques.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.3
• /
• pp.202-207
• /
• 2003

For medical ultrasonic transducer, phase-weighting method has been used for controlling focal length with electric circuit at each vibrating element. However, the electric circuit is complex as the number of vibrating elements is increased. In this paper, we fabricated line-focus transducer with a bimorph-type piezoelectric actuator. The polyvinylidene fluoride (PVDF) piezoelectric type polymer film is used for transmitting and receiving of ultrasonic signal. Using this transducer, focal length of the transducer can be controlled mechanically by changing voltage of the actuator. It is confirmed that focal length of the transducer can be controlled in range of 1095 to radius of curvature.

• Proceedings of the KWS Conference
• /
• 1991.11a
• /
• pp.94-96
• /
• 1991

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.4
• /
• pp.215-222
• /
• 2011

In order to obtain high resolution images, a focusing ultrasonic transducer operated in very high frequency (VHF) range was fabricated and its characteristics were evaluated. A 9-${\mu}m$ thick PVDF film with only one metalized surface for electric ground was adhered to a CCP (Copper-clad polyimide) film by using epoxy. It was pressed by a metal ball to form a concave surface and its rear side was filled with the epoxy. The radius of curvature and the f-number of the fabricated transducer are 7.5 mm and 1.7, respectively. The pulse-echo measurement results from a target located at the focal point showed that the frequency bandwidth was 35.0 MHz and the insertion loss near the peak frequency of approximately 40 MHz was about 60 dB. Those values agreed well with the simulation results by the KLM equivalent circuit analysis including the effect of the epoxy bonding layer. When the image of thin copper lines by the 35 MHz transducer of the UBM (Ultrasonic Backscattering Microscope) system was compared with the image by the transducer fabricated in this study, the fabricated transducer was observed that the axial resolution was improved although the lateral resolution was degraded.

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.4
• /
• pp.164-171
• /
• 2006

If the velocities of longitudinal, transverse and leaky surface acoustic waves in an isotropic material are given, the elastic constants and density of the material can be deduced analytically. Those velocities have been measured using three ultrasonic transducers with different vibrational modes so far. In this paper a line-focusing PVDF transducer with divided electrodes was newly proposed and designed for measuring approximate velocities of the three waves. The measurement method established in this study for each waves using the transducer was applied to several isotropic materials including fused quartz. The elastic stiffness constants and densities of the materials were calculated using the measured velocities, and the accuracies were discussed. It was shown that the obtained results are in good accord with the reference values.

• Smart Structures and Systems
• /
• v.4 no.3
• /
• pp.291-304
• /
• 2008

Piezoelectric materials have been widely used in ultrasonic nondestructive testing (NDT). PZT ceramics can be used to receive and generate surface acoustic waves. It is a common application to attach PZT transducers to the surface of structures for detecting cracks in nondestructive testing. However, not until recently have piezoelectric polymers attracted more and more attention to be the material for interdigitated (IDT) surface and guided-wave transducers. In this paper, an interdigitated gold-on-polyvinylidene fluoride (PVDF) transducer for actuating and sensing Lamb waves has been introduced. A specific etching technology is employed for making the surface electrodes into a certain finger pattern, the spacings of which yield different single mode responses of Lamb waves. Experiments have been performed on steel and carbon fiber composite plates. Results from PVDF IDT sensors have been compared with those from PZT transducers for verification.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.12 no.2
• /
• pp.7-13
• /
• 1992

In this study, we examine the characteristics of beam and the effect of these characteristics on the flaw detection by using different type of two transducers, which are PZT and PVDF film transducer. Consequently, the detection of infinitesimal flaw is more possible than PZT, since it has beam width at focus of $60%{\sim}65%$ in contrast with PZT's. Moreover we can know PVDF transducer has superiority in detecting ability for sub-surface flaw detection in view of its acoustic impedance is near to water's and its focusing range is narrower than PZT's as $65{\sim}85%$ because it has spherical surface.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.2
• /
• pp.112-119
• /
• 2015

Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.