P1J-4 Evaluation of Small Ultrasonic Probe Using Lead Zirconate Titanate Film Deposited by Hydrothermal Method
Recently, our laboratory has explored the possibility of using lead zirconate titanate [PZT] polycrystalline film deposited hydrothermally on titanium substrate to fabricate a small actuator and ultrasound sensor. Hydrothermally deposited PZT polycrystalline films have piezoelectricity without a poling process, and it is easy to deposit PZT polycrystalline films on substrates that are tiny or complexly shaped. We confirmed that hydrothermally synthesized PZT polycrystalline films have wideband frequency characteristics with sensitivities in the megahertz band. It is thought that miniature ultrasound probes with wide- frequency band characteristics can be fabricated using hydrothermally synthesized PZT polycrystalline films. In our last report we assessed methods to produce a miniature ultrasound probe and transceiver characteristics. Here, the reception and transmission directivities of such a probe were measured at 5, 10, 15, and 20 MHz. The results showed that, except at 5 MHz, the theoretical and experimental values agreed. The difference at 5 MHz is attributed to the effect of the resonance frequency of the diameter direction.
Lead Zirconate Titanate Thick-Film Ultrasonic Transducer for 1 to 20 MHz Frequency Bands Fabricated by Hydrothermal Polycrystal Growth
A thickness vibration mode ultrasonic transducer was fabricated by hydrothermal deposition of lead zirconate titanate polycrystalline thick film. This hydrothermal polycrystalline PZT thick-film (HPTF-PZT) ultrasonic transducer was studied for its wide-frequency-band transmission characteristics. The transducer had a 50-µm-thick PZT layer on a 50-µm-thick titanium substrate in an active area of 8 mm×8 mm. The experimental results showed the HPTF-PZT ultrasonic transducer radiated a single ultrasound pulse in the frequency range from 1 to 20 MHz with a 20 dB deviation. Additionally, this transducer generated a 2 MHz sawtooth ultrasonic wave with odd-and even order-harmonic components from the 2nd to the 11th harmonics. These results indicate that the fabricated ultrasonic transducer has satisfactory wide-band characteristics for a MHz frequency range ultrasonic transmitter.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME