• 한국압력기기공학회 논문집
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• 제9권1호
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• pp.8-14
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• 2013

Steam turbine blades and discs of nuclear power plants are one of the most highly stressed areas of turbine rotor, and periodic inspection of the blade roots is essential for monitoring integrity and preventing turbine failure. Ultrasonic technique is applied for volumetric inspection of blade root. However, the complexity of blade root geometry imposes challenges to inspection of blades and discs. Recently, phased array ultrasonic inspection technology is being applied to numerous power generation inspection applications including turbine rotor. The phased array ultrasonic technique requires customized inspection wedges which are generally necessary to generate effectively higher incident angle. But the usage of this wedge can cause access limitation for the lower stage blades of turbine because of the wedge front length. Therefore, the shear wave phased array probe which can generate high inspection angle without wedge is essentially necessary. In this study, feasibility study is conducted for the shear wave phased array ultrasonic probe application to blade and disc inspection. As results, the experimental results show that the shear wave phased array probe can detect the flaw and measure its size with reliable accuracy. Therefore if this shear wave phased array probe is applied to field inspection of blade and disc, more reliable inspection is expected for turbine having access limitation.

• 한국재료학회지
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• 제13권10호
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• pp.651-657
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• 2003

Ultrasonic microscope has been used to detect the defects on surface or inner solid. Conventionally, it has used at a single operating frequency. The resolution and quality of the measured images are determined by a characteristic of the transducer of the ultrasonic microscope. The conventional ultrasonic microscope has been used envelope detector to detect the amplitude of reflected signal, but the changes in amplitude is not sensitive enough for specimen with microstructure that in phase. In this paper, we have studied multi-frequency depth resolution enhancement with ultrasonic reflection microscope for the reflectors of a stainless steel reference specimen and a reference calibration block to be used as the material in nuclear power plants for ISI, PSI. Increased depth resolution can be obtained by taking two, three-dimensional images at more that one frequency and numerically combining the results. As results of the experiment, we could get enhanced images with the rate of contrast in proportion and high quality signal distribution for the image to the changing rate of depth for the reflectors of the two kinds of specimens.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1149-1149
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• 2006

The leakage characteristic is an important factor in power plant. However, most of power plant have efficiency problem which is occurred leaking between high pressure steam turbine axle and stator. The labyrinth seal which is used between the main turbine axle and stator in the power plant. Because it is able to be non-contact seal and it is minimize clearance to decrease the leakage. But its actual system is too huge to experiment. Therefore, most steam turbine seal performance tests were conducted by air similarity test. This paper described a test facility and program for air similarity test of high pressure steam turbine seal. A test facility has been designed and built to evaluate leakage verification of labyrinth seal. The test facility consist of air compressor, anti-swirl labyrinth seal for 1/3 air similarity model, pressure transducer, air flow measure system, instrumentation and auxiliary system. For evaluation of steam turbine seal performance, the air similarity test of labyrinth seal leakage verification was conducted and we compared experiment data and analysis result.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.151-152
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• 2006

Nowadays, great attention has been shown to the question of ultrasonic linear motor for accomplishing the high positioning accuracy and high driving force in the semiconductor and optical industry. Ultrasonic linear motors have many advantages such as simple structure, quick response, ability to maintain position without energy consumption, and electromagnetic effect. And BLT has attracted attention to accomplish large vibration amplitude and large mechanical force. Authors designed and developed the new type of ultra sonic linear motor with multi support mechanism, achieved 75N of output force and 0.45m/s of velocity.

• Journal of Magnetics
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• 제16권3호
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• pp.211-215
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• 2011

The dynamic magnetostriction characteristics of an Fe-based nanocrystalline FeCuNbSiB alloy are investigated as a function of the dc bias magnetic field. The experimental results show that the piezomagnetic coefficient of FeCuNbSiB is about 2.1 times higher than that of Terfenol-D at the low dc magnetic bias $H_{dc}$ = 46 Oe. Moreover, FeCuNbSiB has a large resonant dynamic strain coefficient at quite low Hdc due to a high mechanical quality factor, which is 3-5 times greater than that of Terfenol-D at the same low $H_{dc}$. Based on such magnetostriction characteristics, we fabricate a new type of transducer with FeCuNbSiB/PZT-8/FeCuNbSiB. Its maximum resonant magnetoelectric voltage coefficient achieves ~10 V/Oe. The ME output power reaches 331.8 ${\mu}W$ at an optimum load resistance of 7 $k{\Omega}$ under 0.4 Oe ac magnetic field, which is 50 times higher than that of the previous ultrasonic-horn-substrate composite transducer and it decreases the size by nearly 86%. The performance indicate that the FeCuNbSiB/PZT-8/FeCuNbSiB transducer is promising for application in highly efficient magnetoelectric energy conversion.

• 한국철도학회논문집
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• 제9권3호
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• pp.277-281
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• 2006

The center pivot in the power car of KTX carries the traction force of the motor bogie to the carbody. The damage to the center pivot due to failure of swivel joint causes a serious hazard of the train. To prevent the hazard, information on the relative motion between bogie and carbody is necessary. In this paper, a method to measure the relative rotation of the center pivot is proposed and an actual test to verify the method and safety is conducted. The test results show that the rotation of the center pivot is within the allowable limit and the damage due to the relative motion doesn't take place.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.207-210
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• 1996

This paper describes the analysis of the operation of the switched snubber in order to depress the surge voltage in the MOS-FET inverter. In this paper, the N-channel MOS-FET which operates faster than the P-channel MOS-FET was used for the inverter circuit. So, the inverter and switched snubber can operate at high-frequency in the order of MHz. The cause of generating the surge voltage in the high frequency inverter has been cleared, and then how to depress the surge voltage using the switched snubber consisting of an N-channel MOS-FET has been given. Furthermore, described is the power loss within the switched snubber which is made of an N-channel MOS-FET. The inverter having the N-channel MOS-FET used as a switched snubber can drive such a low impedance load such as mega-sonic transducer for a mega-sonic studied cleaner sufficiently.

• 해양환경안전학회지
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• 제15권3호
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• pp.243-250
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• 2009

연안에서 목적으로 하는 어업에 적합하도록 소형 어군탐지기를 효율적으로 설계하고 평가할 수 있는 방법에 대해 검토하기 위하여 일반적으로 사용되고 있는 어군탐지기의 특성과 탐지범위 등에 대해 조사하였다. 먼저 일반적인 어군탐지기의 빔폭은 주파수와 송신전력이 상승함에 따라 좁아지고 송수파기의 직경은 송신전력이 증가함에 커지는 경향을 보였다. 이 특성을 이용하여 상업적으로 사용되는 일반적인 어군탐지기의 신호대 잡음비를 유도하였다. 탐지거리와 탐지폭으로 구성되는 탐지범위는 이 신호대 잡음비(SN비)로부터 얻을 수 있다. 탐지거리는 주파수의 증가와 함께 증가하였지만 고주파에서는 흡수계수의 영향으로 원거리 탐지가 어려워진다. 즉 송수파기 직경, 송신전력의 증가에 따른 효과는 저주파에서는 크고, 고주파에서는 적은 경향을 보인다. 탐지범위 등을 종합적으로 응용하여 휴대용 어군탐지기의 설계 범용도를 작성하였다. 범용도에는 SN비를 송수파기의 직경, 빔폭, 탐지거리를 변수로하여 주파수에 대해 표시하였다. 범용도에서 SN비가 높고 실용성이 높은 적절한 설계영역을 표시하였다. 설계영역에서 설계점을 정하면 전체적으로 적절한 설계를 할 수 있다. 설계범용도는 어군탐지기의 성능평가에도 응용할 수 있다.

• 비파괴검사학회지
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• 제33권1호
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• pp.26-33
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• 2013

원자로 BMI 노즐은 원자력발전 설비의 운영을 위한 핵심요소 중 하나이며 하부헤드에 설치되어 있다. 상부헤드에 비해 비교적 저온영역에 있지만 최근 외국사례에 비추어 볼 때 PWSCC의 발생 가능성이 크기 때문에 가동중 비파괴검사가 반드시 필요하다. 그러나 BMI 노즐은 원자로 하부에 있기 때문에 고방사선 구역이며 원자로 내부는 붕산수로 채워져 있기 때문에 접근이 매우 어렵다. 본 연구에서 BMI 노즐 검사를 위하여 TOFD를 이용한 탐촉자를 개발하였고, 자동화검사를 위해 내방수 기능을 가진 스캐너를 개발하였다. 또한, BMI 노즐과 동일한 재질 및 형상으로 인공결함시험편을 제작하여 자동화 비파괴검사 시스템의 성능검증을 수행하였다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.242-242
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• 2002

Two MIMAS MaX fuel rods base-irradiated in a commercial PWR have been reinstrumented and irradiated at a test reactor. The fabrication data for two MOX roda are characterized together with base irradiation information. Both Rods were reinstrumented to be fitted with thermocouple to measure centerline temperature of fuel. One rod was equipped with pressure transducer for rod internal pressure whereas the other with cladding elongation detector. The post irradiation examinations for various items were performed to determine fuel and cladding in-pile behavior after base irradiation. By using well characterized fabrication and re-instrumentation data and power history, the fuel performance code, COSMOS, is verified with measured in-pile and PIE information. The COMaS code shows good agreement for the cladding oxidation and creep, and fission gas release when compared with PIE dad a after base irradiaton. Based on the re-instrumention information and power history measured in-pile, the COSMOS predicts re-instrumented in-pile thermal behaviour during power up-ramp and steady operation with acceptable accuracy. The rod internal pressure is also well simulated by COSMOS code. Therfore, with all the other verification by COSMOS code up to now, it can be concluded that COSMOS fuel performance code is applicable for the design and license for MaX fuel rods up to high burnup.