• International Journal of Reliability and Applications
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• 제7권1호
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• pp.27-39
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• 2006

Many real world cases in material failure analysis do not follow perfectly the normal distribution. Forcing of the normality assumption may lead to inaccurate predictions and poor product quality. We examine the failure process of the internal bond (IB or tensile strength) of medium density fiberboard (MDF). We propose a forced censoring technique that closer fits the lower tails of strength distributions and better estimates extremely smaller percentiles, which may be valuable to continuous quality improvement initiatives. Further analyses are performed to build an accelerated common-shaped Weibull model for different product types using the $JMP^{(R)}$ Survival and Reliability platform. In this paper, a forced censoring technique is implemented for the first time as a software module, using $JMP^{(R)}$ Scripting Language (JSL) to expedite data processing, which is crucial for real-time manufacturing settings. Also, we use JSL to automate the task of fitting an accelerated Weibull model and testing model homogeneity in the shape parameter. Finally, a package script is written to readily provide field engineers customized reporting for model visualization, parameter estimation, and percentile forecasting. Our approach may be more accurate for product conformance evaluation, plus help reduce the cost of destructive testing and data management due to reduced frequency of testing. It may also be valuable for preventing field failure and improved product safety even when destructive testing is not reduced by yielding higher precision intervals at the same confidence level.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.43-48
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• 2008

Gear system has been widely used in industrial applications and unexpected failures of gears are not only extremely damaging but also lead to economic losses. So, early detection of fault is important for diagnosis machine condition. And acoustic emission is an efficient non destructive testing technique for the diagnosis of machine health and is useful technique for early detection of fault because it can find low-amplitude and high-frequency signal on account of high sensibility. Therefore, in this paper, the AE signal was measured and preprocessed using envelop analysis for gearbox with misalignment between pinion and gear. And then the vibration characteristic of gear misalignment was analyzed.

• 한국지진공학회논문집
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• 제2권2호
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• pp.77-85
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• 1998

이방성 재료에서의 표면파 진행과 산란에 대한 연구를 수행하였다. 두 개의 이방성 4분 무한 영역의 계면에서의 표면파 산란거동을 해석하기 위한 이론을 제안하였다. Green 함수법을 이용하여 계면에서의 표면파 산란계수를 결정하기 위한 방정식을 유도하였다. 수치계산을 수행하였으며 이방성과 비균질성이 산란 거동에 미치는 영향을 비교하였다.

• Tribology and Lubricants
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• 제11권5호
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• pp.114-121
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• 1995

An ultrasonic technique using normal-incident compressional waves was used to evaluate the surface and subsurface damage in ceramics produced by Hertzian indentation. Damage was produced by a blunt indenter (tungsten carbide ball) in glass-ceramic, green glass and silicon nitride. The damage was classified into two types; (1) Hertzian cone crack, in green glass and fine grain silicon nitride, and (2) distributed subsurface micro fractures, without surface damage, produced in glass ceramic. The ultrasonic technique was successful in detecting cone craks. The measurement results with the Hertzian cone cracks indicated that cracks perpendicular to the surface could be detected by the normal-incident compressional waws. Also shown is the capability of normal-incident compressional waves in detection distributed micro-sized cracks size of subsurface microfractures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.572-577
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• 2011

The acoustic emission (AE) technique is a well-known non-destructive test technique, both in research and for industrial applications. It is mainly used to monitor the onset of cracking processes in materials and components. Predicting and preventing the crack phenomenon has attracted the attention of many researchers and has continued to provide a large incentive for the use of condition monitoring techniques to detect the earliest stages of cracks. In this research, goal is in grasping features of AE signal caused by crack growth. The envelope analysis with discrete wavelet transform (DWT) is used to find the characteristic of AE signal. To estimate feature of divided into three by crack length, the time waveform and the power spectrum were generated by the raw signals and the transferred signal processed by envelope analysis with DWT.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.308-313
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• 1995

Non-destructive inspection techniques using laser have been broading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics and computer. The remarkable inspection technique using laser speckle, so-called ESPI is aleady on the stage of on-line testing with commercial products in other nations. Especially, this technique is expected to be applied to the nuclear industry. Because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringers fso that fringe shift algorthms can be used to determine vibration interferograms recorded by the ESPI system.

• 비파괴검사학회지
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• 제32권3호
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• pp.291-295
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• 2012

In the industrial field, real-time monitoring system like a fault early detection is very important. For this, the infrared thermography technique as a new diagnosis method is proposed. This study is focused on the damage detection and temperature characteristic analysis of ball bearing using the non-destructive infrared thermography method. In this paper, thermal image and temperature data were measured by a Cedip Silver 450 M infrared camera. Based on the results, the temperature characteristics under the conditions of normal, loss lubrication, damage, dynamic loading, and damage under loading were analyzed. It was confirmed that the infrared technique is very useful for the detection of the bearing damage.

• 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.

• Journal of the Optical Society of Korea
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• 제8권1호
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• pp.34-52
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• 2004

Over the past decade the experimental technique of THz time domain spectroscopy (㎔- TDS) has proved to be a versatile method for investigating a wide range of phenomena in the ㎔ or far infrared spectral region from 100 ㎓ to 5 ㎔. This paper reviews some recent results of the Ultrafast ㎔ Research Group at Oklahoma State University using ㎔-TDS as a characterization tool. The experimental technique is described along with recent results on ㎔ beam propagation and how ㎔ beam profiles arise from propagation of pulse fronts along caustics. To illustrate how spatio-temporal electric field measurements can determine material properties over a wide spectral range, propagation of ㎔ pulses through systems exhibiting frustrated total internal reflection (FTIR) are reviewed. Finally two potential metrology applications of ㎔-TDS are discussed, thin film characterization and non-destructive evaluation of ceramics. Although ㎔-TDS has been confined to the research laboratory, the focus on application may stimulate the adoption of ㎔- TDS for industrial or metrology applications.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.233-236
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• 2006

This study presents a technique to quantitatively measure the corrosion level of a reinforcing bar using the infrared thermography system. The temperature-distribution of the concrete surface is monitored and the temperature change of the reinforcing bar is analysed in terms of corrosion level and concrete cover depth. The experimental results indicate that temperature increase of the reinforcing bar is significant when the corrosion level is high, which implies that the quantity of heat is strongly dependent on corrosion level. Also, as the concrete cover depth of the specimen and the atmosphere temperature increase, the temperature variation becomes small.