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Bubyoung Kang 한국비파괴검사학회 2011 한국비파괴검사학회지 Vol.31 No.2
Vibration monitoring is required for reliable thermosonic testing to decide whether sufficient vibration is achieved in each test for the detection of cracks. From a practical point of view, a cheaper and convenient monitoring method is better for the application to real tests. Therefore, the performance of different sensors for vibration monitoring was investigated and compared in this study to find a convenient and acceptable measurement method for thermosonics. Velocity measured by a laser vibrometer and strain provide an equivalent HI when measured at the same position. The microphone can provide a cheaper vibration monitoring device than the laser and the heating index calculated by a microphone signal shows similar characteristics to that calculated from velocity measured by the laser vibrometer. The microphone frequency response shows that it underestimates high frequency components but it is applicable to practical tests because it gives a conservative value of HI.
강부병(Bubyoung Kang) 한국비파괴검사학회 2011 한국비파괴검사학회지 Vol.31 No.2
초음파가진 열화상시험 중 가진 방법이 시편에 가진된 진동의 시스템 응답 특성에 미치는 영향에 대하여 연구하였다. 복잡한 형상을 가진 터빈 블레이드 시편에 가진된 진동의 특성을 분석하기 위하여 고출력의 가진이 가능한 초음파 혼이 사용되었다. 초음파 혼에 입력되는 신호의 특성이 가진된 진동의 특성에 미치는 영향에 대하여 연구하였고 블레이드를 클램프에 고정한 후 가진기와 클램프를 연결하는 방법이 진동 신호에 미치는 영향에 대해서도 연구하였다. 연구 결과를 통하여 첩(chirp) 입력신호와 볼트를 사용하여 클램프와 혼을 연결하는 방법을 가진 방법으로 제안하였다. 이러한 가진 방법은 다양한 종류의 터빈 블레이드 뿐만 아니라 다른 기계부품들의 시험에 적용될 수 있다. The characteristics of the responses obtained in thermosonic tests are investigated in this study to improve the performance of a thermosonic test system. Thermosonic tests are conducted with an acoustic horn with high power capability to investigate the characteristics of the vibration produced in turbine blades with complex geometry. The influences of the excitation signal that is input to the horn and the coupling methods between a clamp and the acoustic horn on the characteristics of the vibration excited in a component are presented. As a result, an excitation method with a fast narrow band chirp test (sweep test) and a stud coupling is proposed as an excitation method for thermosonic testing. This method can be applied to different types of turbine blades and also to other components.
Conceptual Design for HTS Coil in Superconducting Electromagnet for Maglev
Chang Young Lee,Jung Min Jo,Bubyoung Kang,Young Jea Han,Duck Kweon Bae,Yong Soo Yoon,Yoon Do Chung,Sung Yul Chu,Young Jin Hwang,Tae Kuk Ko IEEE 2011 IEEE transactions on applied superconductivity Vol.21 No.3
<P>This study deals with a conceptual design for a high temperature superconductor (HTS) coil fabricated with YBCO wire in a prototype HTS-electromagnet (HTS-EM) model for the electromagnetic suspension (EMS)-based Maglev. Because the size of the HTS coil and the power it consumes during operation are very critical factors in designing the HTS-EM, we focused on the number of coil turns and the operating conditions needed to generate the required magneto-motive force (MMF) effectively. The winding geometry of the sample HTS coil with the largest Ic value was selected for use in this study. To determine the operating condition corresponding to the number of coil turns, we produced the operating profile for the load current of DC current source and the Ic value of HTS coil. From the profile, the optimal number of coil turns to minimize the operating power is determined to be in the range of 1200 to 1400 turns. And the HTS coil should be operated with the current of 37 to 43 A at the cooling temperature of 73 to 76 K.</P>