• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.578-595
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• 2020

Submarine pressure hulls must withstand high hydraulic pressure and be free of defects. To improve the precision of defect detection, we herein examined different probes for optimal defect assessment by applying the Phased Array Ultrasonic Testing (PAUT) method. Two sets of probe design parameters were selected by considering pressure hull characteristics and analyzed through modeling. PAUT probes were applied, and defect assessment results were compared based on ultrasonic signals of various simulated defects in specimens designed to be the same as actual pressure hulls. The final selected design parameters for the submarine probe, which were designed to minimize the grating lobe of wave interference effect and improve the ultrasonic resolution of pressure hull welds, were identified through the experiment. The improvement in the probe's ability to detect defects in a pressure hull was verified. Furthermore, the accuracy of defect length measurement was improved, enhancing the applicability of the technique.

• The Journal of the Acoustical Society of Korea
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• v.29 no.6
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• pp.355-364
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• 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
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• v.32 no.4
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• pp.431-438
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• 2012

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.525-533
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• 2009

Emphasis in the paper is placed on describing guided wave successes and challenges for applications in aircraft and composite materials inspection. Guided wave imaging methods discussed includes line of sight, tomography, guided wave C-scan, phased array, and ultrasonic vibration methods. Applications outlined encircles lap splice, bonded repair patch, fuselage corrosion, water loaded structures, delamination, and ice detection and de-icing of various structures.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.78-82
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• 2010

The feeder pipe of Main Primary Heat Transfer System in Wolsong Nuclear Power Plant was inspected by the Ultrasonic Phase Array technique in 2010. It is the first time to apply this method to the construction at Nuclear Power Plant in Korea. The time required for UT technique is less than RT method. The UT method doesn't need to evacuate personnel who works nearby inspecting area and doesn't need to wait developing of film. For these reasons, the UT method is the fastest method among the volumetric inspections. As a result of the examination, it became clear that main defect of the feeder pipe is the Lack of fusion in the welded area. Moreover, the rate of defect was reduced gradually as improvement of welder's skill. If welding machine has problem, the defect has tended to same pattern(occurred same position in the welding area) but these defects were founded without specific rules. For these reasons, the creation of defect is dependent on the skill of worker not on the automatic welding machine. This evaluation of defect signal and collecting data would be useful to further examination in ISI.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1418-1425
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• 2014

In ultrasonic medical imaging, spatial compounding of images is a technique where ultrasonic beam is steered to examine patient tissues in multiple angles. In the conventional ultrasonic diagnostic imaging, the steering of the ultrasonic beam is achieved electronically using the phased array transducer elements. In this paper, a spatial compounding approach is presented where the ultrasonic probe element is rotated mechanically and the beam steering is achieved mechanically. In the spatial compounding, target position is computed using the value of the rotation axis and the transducer array angular position. However, in the process of the rotation mechanism construction and the control system there arises the inevitable uncertainties in these values. These geometric parameter errors result in the target position error, and the consequence is a blurry compounded image. In order to reduce these target position errors, we present a spatial compounding scheme where error correcting transformation matrices are computed and applied to the raw images before spatial compounding to reduce the blurriness in the compounded image. The proposed scheme is illustrated using phantom and live scan images of human knee, and it is shown that the blurriness is effectively reduced.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.362-368
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• 2012

The objective of this study is to image the harmonic wave generated by contact acoustic nonlinearity in obliquely incident ultrasonic wave for early detection of closed cracks. A closed crack has been simulated by contacting two aluminum block specimens producing solid-solid contact interfaces and then acoustic nonlinearity has been imaged with contact pressure. Sampling phased array(SPA) and synthetic aperture focusing technique(SAFT) are used for imaging techniques. The amplitude of the fundamental frequency decreased with appling pressure. But, the amplitude of second harmonic increased with pressure and was a maximum amplitude at the simulation point of closed crack. Then, the amplitude of second harmonic decreased. As a result, harmonic imaging of contact acoustic nonlinearity is possible and it is expected to be apply for early detection of initial cracks.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.240-249
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• 2018

Purpose: The purpose of this research is to find which technique, between the PAUT (Phased array ultrasonic test) that has been used widely in practice and RT (Radiographic test) that was used widely in the past, has the higher reliability as a non-destructive testing of welding points in water wall tubes. Methods: To evaluated the reliability of non-destructive testing, eleven test pieces that were fabricated intentionally, which have the most frequently occurred defect types in water wall tubes and then both the PAUT and RT were performed on those eleven test pieces to compare their reliability. Results: The differences of type of defect, length are occurred due to the characteristics of nondestructive testing. The RT could not detect the lack of fusion defect type in specimen #4 and #8 while PAUT could not detect the lateral crack and 1 mm size small porosity in specimen #11. Conclusion: It is concluded that applying both the RT and PAUT result the best reliability rather than applying only one test method, if it is possible, in nondestructive testing of weld water wall tube in thermal power plant boiler case.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1581-1582
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• 2015

최근 많은 승객을 수공하는 대중 교통시스템의 안전에 대한 중요성이 더욱 대두되고 있으며, 고속화된 철도차량 또한 이를 피해갈 수 없다. 현재 철도차량의 사고 방지를 위해 많은 연구가 이루어 지고 있으며, 차량기지의 검수설비 및 검수시스템이 자동화되어 많이 발전되었다. 그 중 차축 초음파 탐상은 각 차량기지에 설치된 A-Scan 초음파 방식과 Phased Array 초음파 방식의 두가지 방식의 장비를 이용하여 차축 초음파 탐상이 이루어 지고 있다. 본 논문에서는 초음파 방식 중 철도차량 차축 결함 검출을 위한 A-Scan 탐상 방식과 Phased Array 탐상방식에 대하여 비교 분석하였다.

• 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.