• Title/Summary/Keyword: power transducers

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Acoustic Nonlinearity of Surface Wave and Experimental Verification of Characteristics (표면파의 음향 비선형성과 실험적 특성 검증)

  • Lee, Jae-Ik;Kwon, Goo-Do;Lee, Tae-Hun;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.4
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    • pp.344-350
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    • 2009
  • The goal of this study is to introduce the theoretical background of acoustic nonlinearity in surface wave and to verify its characteristics by experiments. It has been known by theory that the nonlinear parameter of surface wave is proportional to the ratio of $2^{nd}$ harmonic amplitude and the power of primary component in the propagated surface wave, as like as in bulk waves. In this paper, in order to verify this characteristics we constructed a measurement system using contact angle beam transducers and measured the nonlinear parameter of surface wave in an Aluminum 6061 alloy block specimen while changing the distance of wave propagation and the input amplitude. We also considered the effect of frequency-dependent attenuation to the measurement of nonlinear parameter. Results showed good agreement with the theoretical expectation that the nonlinear parameter should be independent on the input amplitude and linearly dependent on the input amplitude and the $2^{nd}$ harmonic amplitude is linearly dependant on the propagation distance.

Development of Ultrasonic Testing System for In-Service Inspection of the Shrunk-on Type LP Turbine Roter (Shrunk-on Type 저압 터빈 로터의 가동중검사를 위한 초음파검사 시스템 개발)

  • Park, Joon-Soo;Seong, Un-Hak;Ryu, Sung-Woo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.2
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    • pp.130-136
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    • 2009
  • Turbine, which is one of major components in nuclear power plants, requires reliable nondestructive inspections. But, accessibility of transducers is limited and interpretation of acquired signals is not easy at all due to the complication. So, in this study, we have fabricated mock-up specimens of real size and shape. we applied pulse-echo method and time-of-flight diffraction(TOFD) method for precise inspection of turbine key and wheel bore. And phased array ultrasonic testing method was adopted for wheel dovetail of turbines by using mock-up. Furthermore, an automatic scanner system was developed for in-service inspection of the developed methods.

Acoustic Nonlinear Characteristics of Ultrasonic Wave Reflected at Contact Interfaces (접촉계면 반사 초음파의 음향 비선형 특성)

  • Park, Byung-Jun;Lee, Tae-Hun;Kim, Chung-Seok;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.1
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    • pp.40-46
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    • 2011
  • In the field application of the conventional acoustic nonlinear technique using through transmission of bulk waves to evaluate the contact acoustic nonlinearity(CAN) in solid-solid contact interfaces like as in the closed crack, it has difficulty to access inner position for attaching the pulsing or receiving transducer. In the present study, a new reflection technique has been suggested to measure the acoustic nonlinearity in solid-solid contact interfaces, which uses both of pulsing and receiving transducers on the same side of target and so that it will be very useful for the field application. For this, based on the linear and the nonlinear contact stiffness estimated by the power-model of the contacting pressure, the nonlinear parameter of the reflected ultrasonic wave at the interfaces has been theoretically calculated. Experimental results in contact interfaces of A1606l-T6 alloy specimens with loading pressure showed good agreement with the theoretical predictions, which proves the validity of the suggested reflection mode technique.

Magneto-inductive Wave in Periodic Chain of Ferrite Cores and Chip Capacitors (페라이트 코어와 칩캐패시터의 주기적 연결구조에서 발생하는 자기유도파)

  • Shin, Kwang-Ho
    • Journal of the Korean Magnetics Society
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    • v.25 no.1
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    • pp.22-26
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    • 2015
  • In this paper, a magneto-inductive wave generated in a chain of LC resonators fabricated with Ni-Zn ferrite cores and chip capacitors is presented. RF signal propagates to neighbor resonator one by one as a consequence of the magnetical coupling between two resonators in the device. The magnetical coupling is due to the mutual inductances along the chain of resonators. So, the signal amplitude (${\approx}$ coupling intensity) is dependent of the mutual inductance which can be adjusted by applied magnetic field. In order to demonstrate the device, some experiments have been carried out systemically. The transmission characteristics of a magneto-inductive wave could be controlled by applied external magnetic field. The device composed of 5 resonators; the center frequencies were estimated to be 32 MHz and 38 MHz with the external magnetic flux density of 75 Oe and 222 Oe, respectively. We expect that the reported results could open a promising way to a high variety of applications in one- and two-dimensional functional devices, such as transducers, delay lines, power dividers and couplers.

Evaluation of high power ultrasonic energy transmission characteristics of a liquid matching layer by using sonoluminescence (소노루미네센스를 이용한 액체정합층의 고출력 초음파에너지 전달특성 평가)

  • Kim, Jungsoon;Kim, Haeun;Son, Jinyoung;Kim, Moojoon
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.5
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    • pp.408-416
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    • 2021
  • In the ultrasonic dispersion, in order to avoid direct contact of the radiation surface of ultrasonic transducers with a liquid sample, the liquid sample is separated by a glass container and it receives ultrasonic energy through an acoustic medium. The transmission efficiency of the ultrasonic energy in the multi-layered ultrasonic system is an important factor. In this study, we suggested a method that can improve the ultrasonic energy transfer efficiency by using a propylene glycol solution as a liquid matching layer in the multi-layered acoustic system. In this method, a propylene glycol solution was filled between the Langevin-type ultrasonic transducer and the luminol solution and the sonoluminescence phenomena in the luminol solution, which is caused by nonlinear effect of high power ultrasound radiated from the transducer, was examined by using a Photo Multiplier Tube (PMT). The transmission efficiency depending on the concentration of propylene glycol solution was observed, and we can see that as the concentration of the propylene glycol solution increased, the matching effect increased while the acoustic attenuation increased. It was confirmed that there is an optimal concentration compromised these two conflicting conditions, and the optimum concentration of the propylene glycol solution was determined experimentally.

Implementation of A Millimeter-Wave Multiflare-Angle Horn Antenna (밀리미터파 다중개구각 혼안테나 구현)

  • Oh, Kyung-Hyun;Kim, Ji-Hyung;Yang, Seung-Sik;Shin, Sang-Jin;Cho, Young-Ho;Lee, Byung-Ryul;Ahn, Bierng-Chearl
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.1
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    • pp.36-41
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    • 2018
  • This paper presents an implementation of a millimeter-wave(W band) multiflare-angle horn antenna. The proposed antenna is a multimode dual-polarized square horn having equal E- and H-plane beamwidths and consists of a multimode generating section, a four-square-waveguide exciter, orthomode transducers, and power combiners for the sum pattern formation. The antenna structure has been designed to allow for easy fabrication and the designed antenna has been fabricated to a precision of ${\pm}0.02mm$ by layer-by-layer machining and diffusion bonding. The input reflection coefficient and the radiation pattern of the fabricated antenna have been measured using a network analyzer and a far-field test facility. Measurements show that the proposed antenna has 17.7~18.3 dBi gain, $25.2{\sim}28.5^{\circ}$ beamwidth, and an input VSWR between 1.02~1.75, within ${\pm}0.5GHz$ from the center frequency.

Evaluation of Ultrasonic Nonlinear Characteristics in Artificially Aged Al6061-T6 (인공시효된 Al6061-T6의 초음파 비선형 특성 평가)

  • Kim, Jongbeom;Lee, KyoungJun;Jhang, Kyung-Young;Kim, ChungSeok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.34 no.3
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    • pp.220-225
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    • 2014
  • Generally, the nonlinearity of ultrasonic waves is measured using a nonlinear parameter ${\beta}$, which is defined as the ratio of the second harmonic's magnitude to the power of the fundamental frequency component after the ultrasonic wave propagates through a material. Nonlinear parameter ${\beta}$ is recognized as an effective parameter for evaluating material degradation. In this paper, we evaluated the nonlinear parameter of Al6061-T6 which had been subjected to an artificial aging heat treatment. The measurement was using the transmitted signal obtained from contact-type transducers. After the ultrasonic test, a micro Vickers hardness test was conducted. From the result of the ultrasonic nonlinear parameter, the microstructural changes resulting from the heat treatment were estimated and the hardness test proved that these estimates were reasonable. Experimental results showed a correlation between the ultrasonic nonlinear parameter and microstructural changes produced by precipitation behavior in the material. These results suggest that the evaluation of mechanical properties using ultrasonic nonlinear parameter ${\beta}$ can be used to monitor variations in the mechanical hardness of aluminum alloys in response to an artificial aging heat-treatment.

Functional beamforming for high-resolution ultrasound imaging in the air with random sparse array transducer (고해상도 공기중 초음파 영상을 위한 기능성 빔형성법 적용)

  • Choon-Su Park
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.3
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    • pp.361-367
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    • 2024
  • Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.