• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1867-1869
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• 2003

In this paper, chamber(Circuit breaker compartment of C-GIS) made of stainless steel with 4 mm width is used. Artificial defect was made on enclosure or HV conductor of chamber and $SF_6$ gas was injected into it according to pressure. In this experiment, Acoustic emission sensors of different types was used to compare sensitivity to detect acoustic signal occurred by Partial discharge(PD) of according to types and resonance frequency in $SF_6$ gas atmosphere. Sensors used in tests was R6I, R15I and 2/4/6 Pre-Amplifier connected with R6IU without pre. amp. In case of R6IU, gain was adjusted with 40 dB like other sensors and operated by differential mode. Post amplifier(post. amp) and band pass filter(BPF) were developed Gain of post. amp. is 60 dB and BPF has band width of $50{\sim}300$ kHz. Also, envelope circuit developed reduces frequency of AE sensor. As a result, in $SF_6$ atmosphere, R6IU and R6I had resonance frequency of 60 Hz was better than R15I. Also, R6IU was better than R6I because of type property of pre.amp. had differential mode.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.197-205
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• 2015

The Diamond Like Carbon(DLC) films for the Electro Optical Tracking System(EOTS) by using Plasma Enhanced Chemical Vapor Deposition(PECVD) method is presented. We achieve that the DLC films can reduce the surface delamination of thermal observation sensor front window due to the high hardness, low friction and chemical inertness which is comparable to a Si film. According to our experiment results, DLC films can be used for various electro optical systems to eliminate surface delamination.

• Journal of the Korean Society for Nondestructive Testing
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• v.8 no.1
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• pp.12-21
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• 1988

The behaviour of pressure vessel made of SS41 steel was investigated during hydrotest. AE tests were carried out for the vessels in as-manufactured, V-notched and weld-cracked state using microcomputer-based AE instrumentation. The following results were obtained: 1) In the case of source location using cylindrical program, to minimize the error of source location, the difference of max. Delta T values measured from each sensor should be kept as small as possible. 2) When crack grew, AE event rate increased continuously but AE event from the inclusions occurred intermittently, so by analyzing event rate, the source of AE could be derived. 3) From the spot welding part of supporter, many events with low energy occurred independent of Kaiser effect, which could be confirmed by analyzing energy parameter. 4) The b-value from the tensile specimen of was lower than that from normal specimen and the b-value from crack propagation was lower than that from deformation, so by analyzing peak amplitude distribution, the source mechanism could be derived from the b-value.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.395-399
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• 2007

Renewable energy sources such as wind energy is copiously available without any limitation. Wind turbines are used to tap the potential of wind energy which is available in millions of megawatt. Reliability of wind turbine is critical to extract this maximum amount of energy from the wind. We reviewed different techniques, methodologies, and algorithms developed to monitor the performance of wind turbine as well as for an early fault detection to keep away the wind turbines from catastrophic conditions due to sudden breakdowns. To keep the wind turbine in operation, implementation of Condition Monitoring System (CMS) is paramount, and for this purpose ample knowledge of these types of system is mandatory. So, an attempt has been made in this direction to review maximum approaches related to CMS in this piece of writing.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.3
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• pp.118-126
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• 2002

TiCN thin films were deposited on tool steels at $510^{\circ}C$ by PECVD from a $TiCl_4+N_2+CH_4+H_2+Ar$ gaseous mixture. The microstructures and preferred orientation were investigated. The micro-scratch tests were performed using a system equipped with an acoustic emission sensor. Critical loads were determined to evaluate the adhesion of TiCN to substrate. The influences of the microstructures of substrates, double layered coatings, and coatings after nitriding(duplex coating) were investigated. The experimental results showed that the microstructures of substrates and double layered coating did not affect the critical loads considerably. By the duplex coating, critical loads were not always increased. In some cases, duplex coatings decreased critical loads significantly despite of absence of black layer. In this study, we tried to relate the results of scratch test to the residual stress analysis. Nitriding before the coating reduces the tensile residual stress in the film, which gives rise to low critical load in scratch test.

• International Journal of Railway
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• v.1 no.1
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• pp.1-5
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• 2008

The railway system requires safety and reliability of service of all railway vehicles. Suitable technical systems and working methods adapted to it, which meet the requirements on safety and good order of traffic, should be maintained. For detection of defects, non-destructive testing methods-which should be quick, reliable and cost-effective - are most often used. Since failure in railway wheelset can cause a disaster, regular inspection of defects in wheels and axles are mandatory. Ultrasonic testing, acoustic emission and eddy current testing method and so on regularly check railway wheelset in service. However, it is difficult to detect a crack initiation clearly with ultrasonic testing due to noise echoes. It is necessary to develop a non-destructive technique that is superior to conventional NDT techniques in order to ensure the safety of railway wheelset. In the present paper, the new NDT technique is applied to the detection of surface defects for railway wheelset. To detect the defects for railway wheelset, the sensor for defect detection is optimized and the tests are carried out with respect to surface and internal defects each other. The results show that the surface crack depth of 1.5 mm in press fitted axle and internal crack in wheel could be detected by using the new method. The ICFPD method is useful to detect the defect that initiated in railway wheelset.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.211-216
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• 2016

Al alloys are useful materials having high specific strength and are used in machining of parts having thin-walled structures for weight reduction in aircraft, automobiles, and portable devices. In machining of thin-walled structures, it is difficult to maintain dimensional accuracy because machining deformation occurs because of cutting forces and heat in the cutting zone. Thus, cutting conditions and methods need to be investigated and cutting signals need to be analyzed to diagnose and minimize machining deformation and thereby enhance machining quality. In this study, an investigation on cutting conditions to minimize machining deformation and an analysis on characteristics of cutting signals when machining deformation occurs are conducted. Cutting signals for the process are acquired by using an accelerometer and acoustic emission (AE) sensor. Signal characteristics according to the cutting conditions and the relation between machining deformation and cutting signals are analyzed.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1940-1945
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• 2007

The wheelsets are one of most important component: damages in wheel tread and press fitted axle are a significant cost for railway industry. Since failure in railway wheelset can cause a disaster, regular inspection of defects in wheels and axles are mandatory. Ultrasonic testing, acoustic emission and eddy current testing method and so on regularly check railway wheelset in service. However, it is difficult to use this method because of its high viscosity and because its sensitivity is affected by temperature. Also, due to noise echoes it is difficult to detect defects initiation clearly with ultrasonic testing. It is necessary to develop a non-destructive technique that is superior to conventional NDT techniques in order to ensure the safety of railway wheelset. In the present paper, the new NDT technique is applied to the detection of surface defects for railway wheelset. To detect the defects for railway wheelset, the sensor for defect detection is optimized and the tests are carried out with respect to surface and internal defects each other. The results show that the surface crack depth of 1.5 mm in press fitted axle and internal crack in wheel could be detected by using the new method. The ICFPD method is useful to detect the defect that initiated in the tread of railway wheelset.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.3
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• pp.24-31
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• 2004

A successful on-line monitoring system for conventional machining operations has the potential to reduce cost, guarantee consistency of product quality, improve productivity and provide a safer environment for the operator. In fine-shape machining, typical signs of tool problems such as vibration, noise, chip flow characteristics and visual signs are almost unnoticeable without the use of special equipment. These characteristics increase the importance of automatic monitoring in fine-shape machining, however, sensing and interpretation of signals ar more complex. In addition, the shafts of the mini-tools break before the typical extensive cutting edge of the tool gets damaged. In this study, the existence of a relationship between the characteristics of the cutting force and tool usage was investigated, and tool breakage detection algorithm by LabVIEW was developed and the following results are obtained. It was possible to use a relative error compare which mainly used in established experiment and investigated tool breakage detection algorithm in time domain which can detect AE and cutting force signals more effective and accurate.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.407-412
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• 2001

In this research, damage behavior of singly oriented ply (SOP) fiber metal laminate (FML) subject to concentrated load was studied. The static indentation tests were conducted to study fiber orientation effect on damage behavior of FML. During the static indentation tests, Acoustic Emission technique (AE) was adopted to study damage characteristics of FML. AE signals were obtained by using AE sensor with 150kHz resonance frequency and the signals were compared with indentation curves of FML. As fiber orientation angle increases, the crack initiation load of SOP FML increases because the stiffness induced by fiber orientation is increased. The penetration load of SOP FML is influenced by the deformation tendency and boundary conditions. Cumulative AE counts were well predicted crack initiation and crack propagation and AE amplitude were useful for prediction of damage failure mode. During the matrix cracking, fiber debonding and fiber breakage, AE amplitude has $45{\sim}60dB,\;60{\sim}80dB\;and\;90{\sim}100dB$, respectively.