• Journal of the Korean Society for Nondestructive Testing
• /
• v.26 no.4
• /
• pp.231-238
• /
• 2006

Nondestructive examination for low pressure turbine disc in standard nuclear power plant using phased array technique was studied. For this purpose, disc mockups were made and notches were machined in the mockups. Detection and length sizing by different methods are compared. Depth of deep notches could be measured by using AATT(absolute arrival time technique) or RATT(relative arrival time technique) but shallow notches that must be detected in early stage couldn't be measured by these two methods. For this case, notch depth was estimated by using signal response angle range and preyed usefulness.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.1
• /
• pp.15-20
• /
• 2009

The results of crack evaluation by conventional UT(Ultrasonic Test)is highly depend on the inspector's experience or knowledge of ultrasound. Phased array UT system and its application methods for small crack length evaluation will be a good alternative method which overcome present UT weakness. This study was aimed at checking the accuracy of crack length evaluation method by electronic scanning and discuss about characteristics of electronic scanning for crack length evaluation. Especially ultrasonic phased array with electronic scan technique was used in carrying out both sizing and detect ability of crack as its length changes. The response of ultrasonic phased array was analyzed to obtain the special method of determining crack length without moving the transducer and detect-ability of crack minimal length and depth from the material. A method of crack length determining by electronic scanning for the small crack is very real method which has it's accuracy and verify the effectiveness of method compared to a conventional crack length determination.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.490-490
• /
• 2023

위상배열초음파검사(PAUT)는 기존 초음파검사에서 획득할 수 있었던 A-scan의 결과와 달리, 관로 내부로 진입하지 않고도 부식에 의한 강관 손상 정도를 정량적인 시각적 데이터로 파악할 수 있는 검사 기술이다. 관내부 직접조사가 가능한 상수도 강관을 대상으로 직접조사와 PAUT를 비교한 결과, PAUT는 높은 정확도와 신뢰성을 보여주었다. 또한, 강관 내부의 부식검사에서는 PAUT를 적용함으로써 관체의 부식 면적, 부식 최대 깊이, 부식 위치를 넓은 범위에서 신뢰성 높은 검사 및 결과 도출이 가능하였다. 이러한 결과는 PAUT 기술이 강재 구조물의 다양한 부식 문제를 신속하게 파악하고 해결하는 데 기여할 수 있음을 의미한다. 따라서, 본 검사 기법은 상수도 관로의 강재 진단 및 점검에 있어 높은 신뢰성 및 효율성을 보여 주는 진단기법으로써 다양한 강재 시설물의 평가에 활용성이 클 것으로 판단된다. 이에 따라 PAUT는 상수도 시설물뿐만 아니라 다양한 시설물에서도 높은 활용 가능성을 가질 것으로 예상된다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.4
• /
• pp.368-375
• /
• 2013

Failure of small bore piping welds is a recurring problem at nuclear power plants. And the socket weld cracking in small bore piping has caused unplanned plant shutdowns for repair and high economic impact on the plants. Consequently, early crack detection, including the detection of manufacturing defects, is of the utmost importance. Until now, the surface inspection methods has been applied according to ASME Section XI requirements. But the ultrasonic inspection as a volumetric method is also applying to enforce the inspection requirement. However, the conventional manual ultrasonic inspection techniques are used to detect service induced fatigue cracks. And there was uncertainty on manual ultrasonic inspection because of limited access to the welds and difficulties with contact between the ultrasonic probe and the OD(outer diameter) surface of small bore piping. In this study, phased array ultrasonic inspection technique is applied to increase inspection speed and reliability. To achieve this object, the 3.5 MHz phased array ultrasonic transducer are designed and fabricated. The manually encoded scanner was also developed to enhance contact conditions and maintain constant signal quality. Additionally inspection system is configured and inspection procedure is developed.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.6
• /
• pp.355-364
• /
• 2010

Considering biological safety, it is very important to measure acoustic power from ultrasonic array probe for diagnostic ultrasound imaging applications. In this paper, to measure acoustic power from each element on array probe for ultrasonic diagnostic equipment, we reconstruct and automate the acoustic power measurement system. The acoustic power from linear, phased and curved array were measured and analyzed. As a result of measurement, the effects caused by directivity of sound beam from curved array were founded. To remove these effects, we developed and applied the correction model. The proposed system is useful to evaluate characteristics of the acoustical output power of array probe.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.6
• /
• pp.538-544
• /
• 2000

A phased array ultrasonic nondestructive inspection system is being developed to obtain images of the interior of steel structures by modifying a medical ultrasound imaging system. The medical system consists of 64 individual transceiver channels that can drive 128 array elements. Several modifications of the system were required mainly due to the change of sound speed. It was necessary to fabricate array transducers for steel structure and to obtain A-scan signal that is necessary for the nondestructive testing. Boundary diffraction wave model was used for the prediction of radiation beam field from array transducers, which provided guidelines to design array transducers. And a RF data acquisition board was fabricated for the A-scan signal acquisition along a selected un line within an image. For the proper beam forming in the transmission and reception for steel structure, delay time was controlled. To demonstrate the performance of the developed system and fabricated transducers, images of artificial specimens and A-scan signals for selected scan lines were obtained in a real time fashion.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.3
• /
• pp.361-367
• /
• 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.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.18 no.6
• /
• pp.604-613
• /
• 2009

Recently, researches to develop phased array ultrasonic examination techniques are proceeded to diagnose dental caries and the status of surgical operation of dental implant. Sound field analysis of phased array ultrasonic transducers were carried out in order to characterizing the ultrasonic phased array beams. The sound field of ultrasonic radiation was calculated for the sample called "gypsum-improved stone" with the similar characteristics of dental materials. Industrial phased array ultrasonic devices were utilized for the insptriion of the artificial flaws machined in the gypsum-improved stone. Dental implants were made at the pig jaw bone and defect images were confirmed for the dental implants.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.902-903
• /
• 2011

발전설비에 대한 비파괴 검사 기술은 발전소 운전 신뢰성 및 안전성 유지확보 그리고 건전성을 보장하기 위한 필수적인 기술이다. 이 설비 중 터빈, 보일러 등 주요 발전설비에 대한 초음파 검사는 매우 신중하고 정확하게 검사할 필요성이 있으나, 일반적 초음파 검사방법으로는 불가능한 부분이 많고 일부분에 대해서는 이를 외국 제작사 기술용역에 의존하고 있는 실정이다. 특히 발전기 로타 웨지와 같이 재질상 감쇄가 심한 재료에 대해서는 검사 자체가 어렵고, 지금의 초음파 검사 방법으로는 결함의 크기나 형태를 파악하기도 어려워 이에 대한 개선책이 시급한 실정이다. 최근에 개발이 시작된 Phased Array UT분야는 발전설비중 접근자체가 어렵고, 형상이 복잡하여 결함의 탐지 및 평가가 힘든 부분에 적용하면 검사신뢰도 및 신속성을 향상시킬 수 있으며 접근성에 대한 제한 또한 감소시킬 수 있다. 따라서 본 논문은 발전기 부품에 발생하는 일반적인 결함에 대하여 Phased array UT 기술을 도입하여 신호의 특성을 분석하는 결과평가에 도음이 되고자 하였다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.2
• /
• pp.130-136
• /
• 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.