• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.337-339
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• 2007

본 논문에서는 유한요소 해석 소프트웨어를 이용하여 연질금속을 접합할 수 있는 초음파 금속용접기용 트랜스듀서를 개발하였다. 개발된 트랜스듀서는 35kHz의 공진 주파수의 특성을 갖게 설계하였으며 트랜스듀서 플랜지의 종축변위가 최소가 되도록 설계하였다. 볼트체결형 트랜스듀서는 결속력에 따라 기계적 Q값이 변동되어 출력에 많은 영향을 준다. 따라서 특성 실험을 통하여 트랜스듀서에 대한 체결토크를 최적화하였다.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.109-117
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• 1994

Spot welding has wide used with a high work efficiency in the automotive and aerospace industries. Up to the present, the technique mainly used to test spot welds on production lines has been entirely depended upon destructive chisel or peel testing. Therefore, it's being very important assignment to secure the NDE technique which can be evaluate spot weld quality with more efficiency and high reliability. This paper discusses the feasibility of UNDE techniques to evaluate spot weld quality. For the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of a the corona bond from nugget, ultrasonic c-scan image and distribution of reflective echo amplitude was measured by immersion method with the mechanical and the electronic scanning of point-focussed ultrasonic beam(25 MHz). As the results of this study, corona bond which is the most dangerous types of interface defects can be successfully detected, as well as expulsion and voids. Ultrasonic testing results were confirmed and compared by optical microscope and SAM(Scanning Acoustic Microscope) observation of the spot-weld cross section. The results show that the nugget diameter can be successfully measured with the accuracy of 0.8 mm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.10-16
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• 2011

A cabinet is an outer frame of a TV, which is usually made of poly-carbonate. Cabinets are apt to be deformed because of applied heat during injection molding process and UV joining process. Severely deformed cabinets cause a falling-off in quality of the final product. Therefore cabinets should be inspected and only the good ones should be delivered to the following process. We implemented an experimental system for shape recognition of a cabinet and proposed several indices to characterize the shape of a cabinet. We also proposed algorithms to eliminate the possible bias present in measured data and to check the goodness of a cabinet. Experimental results show the feasibility of the propose algorithms.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.20-25
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• 2013

Ultrasonic methods are widely used to degradation assessment. Remaining-life cycle of metal can be estimated by ultrasonic parameters because ultrasonic velocity and attenuation are affected by change of material properties with accumulated fatigue in the metal. Therefore, in this study, we will estimate overall change of material properties by 2D C-scan image. Fatigued aluminum alloy 6061-T6 samples from 0 to 85% were prepared for evaluating fatigue life cycle. Also, degraded image of materials using attenuation is proposed to estimate degree of material degradation for determining degraded area of fatigued samples. Finally, we will predicts process pf degradation with measured attenuation of fatigued aluminum alloy 6061-T6 samples.

• Food Science and Preservation
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• v.19 no.3
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• pp.323-327
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• 2012

The effects of ultrasound and ascorbic acid cotreatment on the browning inhibition and microbial growth of fresh-cut Tsugaru apples were investigated. The prepared samples were dipped in distilled water (Cont) or 1% (w/v) ascorbic acid solution (AA) and were then ultrasonicated in distilled water (US) or 1% (w/v) ascorbic acid solution (AA+US). The samples were then packed in a 0.04mm polypropylene bag ($20{\times}15$ cm) and were stored at $10^{\circ}C$ for eight days. The AA+US treated samples showed high $L^*$ and low $a^*$, $b^*$ values as well as inactivated PPO activity. The growth of the total aerobic bacteria also inhibited the AA+US treated samples more. The physicochemical properties were not different among all the samples. It was demonstrated in this paper that the ultrasonication treatment with ascorbic acid prevented the enzymatic browning of and microbial growth in fresh-cut Tsugaru apples.

• Journal of Welding and Joining
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• v.27 no.5
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• pp.68-73
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• 2009

The bar horn is designed to increase uniformity of the displacement on the output face through simulation and experiments. Three-dimensional modal analysis is conducted using the finite element method to calculate the vibration mode and displacement on the output face, and the design of experiment (DOE) technique is employed to determine the optimum dimensions of the groove and slot so that the high amplitude uniformity of the bar horn is produced. Displacement of the bar horn was measured using the Laser Doppler Vibrometer (LDV), and the experimental results show good agreements with the predicted results. High uniformity of the bar horn is achieved with the dimensions of the groove and slot determined using the design equations.

• Archives of Reconstructive Microsurgery
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• v.4 no.1
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• pp.1-8
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• 1995

장시간 허혈상태의 토끼 이개를 실험대상으로 하여 유로키나제와 헤파린을 병용 또는 단독으로 사용시와 또한 약물을 사용하지 않았을 때, 이들이 모세혈관의 개존성과 아울러 미세수술후의 조직 생존율에 미칠 수 있는 효과를 보기 위하여 허혈상태의 토끼 이개를 미세수술로 접합한 후 모세혈관으로의 혈류를 측정하기 위하여 레이저 초음파 혈류측정기(Laser doppler flowmetry)를 이용하였으며 방사선 구슬들(Cobalt-57 with plastic material with average diameter 15 micron)을 주입한 결과 유로키나제 조합에서 통계적으로 유효한 성적을 얻었다. 광학현미경 소견은 유로키나제와 헤파린을 병용한 조합에서 모세혈관내 내피세포의 배열이 유지되어 있었으며 헤파린을 사용한 조합에서도 유사한 소견을 보였으나 약물을 사용하지 않은 조합에서는 국소적인 내피세포의 배열이 결핍되어 있었다. 전자현미경 소견에서 유로키나제와 헤파린을 병용한 조합에서 내피세포가 혈관내벽에 배열되어 있었고 또 불규칙한 세포질이 돌출되어 있었다.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.148-150
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• 2006

In this paper, the applicability of an UET(ultrasound excited thermography) for a defect detection of the welded receptacle is described. An UET(ultrasound excited thermography) is a defect-selective and fast imaging tool for damage detection. A high power ultrasound-excited vibration energy with pulse durations of 280ms is injected into the outer surface of the welded receptacle made of Al material. An ultrasound vibration energy sent into the welded receptacle propagate inside the sample until they are converted into the heat in the vicinity of the defect. The injection of the ultrasound excited vibration energy results in heat generation so that the defect is turned into a local thermal wave transmitter. Its local heat emission is monitored by the thermal infrared camera. And they are processed by the image recording system. Measurement was performed on aluminum receptacle welded by using Nd:YAG laser. The observed thermal image revealed two area of defects along the welded seam.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.307-309
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• 2006

For efficient NDE of pipes, essential components of power plant facilities, ultrasonic guided waves were generated and received applying an air-coupled transducer and comb one as non-contact technology, Mode generation and selection were predicted based on theoretical dispersive curve and the element spaceof a comb transducer. In addition, a receiving angle of the air-coupled transducer was determined to acquire the predicted modes by theoretical phase velocity of each mode. Theoretical dispersive curve was compared with the results of the time-frequency spectroscopes based on the wavelet transform and 2D-FFT to identify the characteristics of the received mode. The received modes show a good agreement with the predicted ones.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.305-307
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• 2004

One set of rotor coils is required per each large generator rotor assembly, Rotors consist of two directly opposing poles. Each pole requires from 5 to 9 coils. Each coil is made up of two halves identified on the connection end. These coil halves will be joined together by butt brazing process during subsequent rotor assembly. Each half coil is made up of typically 4 to 9 layers of copper conductors. Because of Generator rotor is rotated very high speed with 3,600RPM, the quality soundness of brazed joints is very important at each coil. But, it is very difficult to be optimized non-destructive evaluation, because c-coil has the long shape and evaluation is to be done assembled condition. In this paper introduce newly developed inspection process and acceptance standards for the ultrasonic inspection of " C" coil butt braze. This inspection system is a semi-automatic ultrasonic flaw detector with data acquisition and retention capable of assessing the relative lack of bond of brazed butt joints