• 한국항공우주학회지
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• 제37권8호
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• pp.780-788
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• 2009

복합재 날개 구조물에 대한 구조 건전성 및 손상을 평가하기 위하여 정적 구조강도시험에 음향방출(AE)법이 응용되었다. 시험중 스트레인과 변위측정기법을 통하여 정적구조강도를 확인하였고, 음향방출요소 분석과 위치표정기법을 통하여 구조물의 내부 손상을 평가하고 손상위치를 찾을 수 있었다. 시험은 설계제한하중시험, 2차에 걸친 설계극한 하중시험, 파단시험이 수행되었다. 주요한 AE신호는 front lug근처의 표면에 부착된 센서에 의하여 감지되었다. 특히 1차 설계극한하중시험에서 스트레인 및 변위결과는 내부 손상을 보이지 않았으나 AE신호는 내부 손상이 이미 형성된 현상을 나타내었다. 파단시험에서는 AE활성도가 매우 활발하였고, 스트레인 및 변위의 결과는 심한 손상에 의하여 하중경로가 바뀌는 경향을 나타내었다. 음향방출법을 적용하여 정적 구조시험이 진행되는 동안 내부손상이 발생되는 하중과 위치를 정확하게 평가할 수 있었다. 본 연구로부터 음향방출법은 정적 구조강도시험에 있어 내부 손상을 평가하는데 유용한 기법임이 확인되었다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.268-271
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• 2001

When compared to other composite materials such as FRP and MMC, hybrid composite material is more attractive one due to the high specific strength and the resistance to fatigue. However, the fracture mechanism of hybrid composite material is extremely complicated because of the bonding structure of metals and FRP. Recently, nondestructive technique has been used to evaluate the fracture mechanism of these composite materials. In this study, AE technique has been used to clarify the fracture mechanism and the degree of damage for Al 7075/CFRP hybrid composite material. It was found that AE event, energy and amplitude among AE parameters were effective to evaluate fracture process of Al 7075/CFRP composite material. In addition, the relationship between the AE signal and the characteristics of failure surface using optical microscope was discussed.

• Smart Structures and Systems
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• 제13권1호
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• pp.155-171
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• 2014

Various monitoring techniques are now available for structural health monitoring and Acoustic Emission (AE) is one of them. One of the major advantages of the AE technique is its capability to locate active cracks in structural members. AE crack locating approaches are affected by the signal attenuation and dispersion of elastic waves due to inhomogeneity and geometry of reinforced concrete (RC) members. In this paper, a novel technique is described based on signal processing and sensor arrangement to process multisensory AE data generated by the onset and propagation of cracks and is validated with experimental results from an in-situ load test. Considering the sources of uncertainty in the AE crack location process, a methodology is proposed to capture and locate events generated by cracks. In particular, the relationship between AE events and load is analyzed, and the feasibility of using the AE technique to evaluate the cracking behavior of two RC slab strips during loading to failure is studied.

• 한국해양공학회지
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• 제13권4호통권35호
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• pp.98-104
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• 1999

The crank shafts need anti-corrosion materials. So STS 304 is the essential material to manufacture this shaft. However, it costs more to manufacture the shafts by using only STS 304 than welding of STS 304 to other carbon steels. And it has been difficult to weld this sort of dissimilar materials. They could be unstable in the quality by the conventional arc welding. And also they have a lot of technical problems in manufacturing. But by the friction welding technique, it will be able to be made without such problems. Then, this study aimed not only to develop the optimization of dissimilar friction welding of crank shafts steels of STS 304, SM35C, but also to develop the application technique of the acoustic emission to accomplish in-process real-time quality(such as tensile) evaluation during friction welding of the shafts by the AE technique.

• 한국정밀공학회지
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• 제2권1호
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• pp.62-71
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• 1985

This is a study on the monitoring technique in tool failure and tool life by AE method. The relation between amplitude level of AE signal and flank wear width was studied by experiments. The relation between amplitude level of AE signal and tool life was also studied. As the result, it was observed that amplitude level of AE signal was only affected by cutting velocity. Amplitude level of AE signal was directly proportional to flank wear width and the increasing rate was related to cutting velocity. So, the relation between amplitude level of AE signal and tool life was represented as follow: $CT^n$ = $AE_{rms}$ where, n=0.35 C=9.5*$10^{-2}$

• 한국초전도ㆍ저온공학회논문지
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• 제1권2호
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• pp.8-14
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• 1999

In this study, acoustic emission(AE) technique has been applied to detecting quench which is one of the serious peoblems to assure the integrity of superconducting coil at cryogenic temperature. The characteristics of AE parameters have been analyzed by correlating with the number of quenches, whinding tension of superconducting coil and charge rate of transport current. The quench localization was also performed using AE signals and there was also good correlation between quench current and AE parameters such as AE energy and AE events. In this study, it was confirmed that AE signals were mainly due to the conductor motion which caused by premature quenching. It was also found that optimized winding tension at superconducting coil was needed to prevent quench caused by conductor motion.

• 동력기계공학회지
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• 제14권6호
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• pp.41-46
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• 2010

Acoustic emission (AE) technique is a well-known non-destructive test technique. Fatigue crack growth test was performed using SM53C to check up the AE signal occurred by crack growth, so AE system was used to detect the crack signal. Features calculated by the AE signals were analyzed to evaluate the steps divided the crack growth into three. The steps, initiation, growth and breaking, were separated by velocity of the crack growth. Time waveform and power spectrum were created by the AE signal of each one of the steps and compared. In the feature domains, it was found that AE values changed rapidly as the velocity of the crack increasing.

• 동력기계공학회지
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• 제6권2호
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• pp.48-53
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• 2002

Plunger (piston rod) materials are used in high-pressure condition. So STD11 is the essential material to build this plunger. However, it costs more to make a plunger by using only STD11 than using the welding of STD11 to SCM440 and other dissimilar material. And it has been difficult to weld this sort of dissimilar materials. They could be unstable in the quality by the conventional arc welding. And also they have a lot of technical problems in manufacturing. But, by the friction welding technique, it will be able to be made without such problems. And then, on account of such reasons, we need a new approach of study on real-time quality evaluation by acoustic emission (AE) techniques as well as a domestic development of the plunger by friction welding. So that, the purpose of this study for such developments is the development of a plunger by optimizing of friction welding with more reliability and more applicability. Then, this study aimed not only to develop the optimization of friction welding of dissimilar plunger steels of STD11 to SCM440, but also to develop the application technique of the acoustic emission to accomplish an in-process real-time quality evaluation during friction welding of the plunger materials by the AE technique.

• 터널과지하공간
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• 제18권1호
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• pp.1-9
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• 2008

미소파괴음(Acoustic Emission, AE)과 미소지진음(Microseismic event, MS event)은 응력의 재분배에 의한 균열이 생성될 때 나오는, 순간적인 에너지 방출에 의한 탄성파이다. AE/MS 이벤트는 일반적으로 대규모의 파괴에 앞서 그 발생이 현저해지는 경향이 있다. 이들은 계측영역의 주파수 대역에 따라 구분되며, MS이벤트에 비해 상대적으로 고주파의 AE 신호는 보다 미세한 파괴를 검출할 수 있다. 일반적으로 암반구조물은 파괴되기까지 작은 변형이 발생하여 종래에 사용되고 있는 변위계측으로는 그 전조현상을 포착하기 어렵기 때문에 국부적인 파괴나 갑작스러운 파괴에 대한 사전예측이 어려운 현실이다. 그러나 AE/MS 이벤트의 파형을 측정할 수 있는 경우 암반구조물의 파괴를 사전에 예측할 수 있으며, 초동이 명확한 경우 미세한 파괴위치지점과 함께 파괴메커니즘의 규명도 가능하다. 본 보고에서는 AE/MS 이벤트에 대한 기본이론과 함께 이들 활용한 계측기술 개발현황과 적용사례 등을 소개한다.

• 한국공작기계학회논문집
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• 제13권4호
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• pp.95-99
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• 2004

In this study, the leak detection technique of pressure vessel by using acoustic emission(AE) signal is suggested experimentally. The leak of pressure vessel is located at the welding line due to welding defects. we measured the AE signal using Rl5I sensor, and examined the AE parameters in leak condition. It is investigated that the mean value of AE signal is dependent on leak source location. So the absolute mean value of AE signal is adopted as dominant AE parameter. We proposed leak detection algorithm using AE signal mean value for monitoring the leak source location.