• 비파괴검사학회지
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• 제29권6호
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• pp.563-569
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• 2009

In this paper, four different types of pulsed eddy current(PEC) probe are designed and their performance of detecting wall thickness reduction is compared. By using the backward difference method in time and the finite element method in space, PEC signals from various thickness and materials are numerically calculated and three features of the signal are selected. Since PEC signals and features are obtained by various types and sizes of probe, the comparison is made through the normalized features which reflect the sensitivity of the feature to thickness reduction. The normalized features indicate that the shielded reflection probe provides the best sensitivity to wall thickness reduction for all three signal features. Results show that the best sensitivity to thickness reduction can be achieved by the peak value, but also suggest that the time to peak can be a good candidate because of its linear relationship with the thickness variation.

• 플랜트 저널
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• 제7권3호
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• pp.65-73
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• 2011

This research has suggested a method to select pipe wall thickness by application of the value engineering to reduce the cost and quantity that are major part of construction materials. This research shows that the application of value engineering reduces the cost of piping materials by optimizing pipe wall thickness while maintaining process flow date of design pressure and design temperature. Based on this knowledge, the application of the value engineering will lead to the cost reduction and quantity reduction by effective selection of pipe wall thickness. The application of the value engineering will help the EPC companies to win a contract in the overseas plant market.

• 소성∙가공
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• 제20권6호
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• pp.432-438
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• 2011

A method for estimating the shear spinnability is suggested, and it was applied to sheets of Ti-6Al-4V alloy for estimation of shear spinnability at hot working temperature. The effective working temperature was $850^{\circ}C$ or above. The hot spinning operation was carried out in two steps of shear spinning. The reduction of thickness at the first step was 50% and 45% at the second, and the overall reduction of thickness was 72.4%. The cone spinning process could produce a uniform wall thickness with only a few percent tolerance, proving itself appropriate for making cones of Ti-6Al-4V alloy with uniform wall thickness.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2119-2129
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• 2020

Flow-accelerated corrosion (FAC), liquid droplet impingement erosion (LDIE), cavitation and flashing can cause continuous wall-thinning in nuclear secondary pipes. In order to prevent pipe rupture events resulting from the wall-thinning, most NPPs (nuclear power plants) implement their management programs, which include periodic thickness inspection using UT (ultrasonic test). Meanwhile, it is well known in field experiences that the thickness measurement errors (or deviations) are often comparable with the amount of thickness reduction. Because of these errors, it is difficult to estimate wall-thinning exactly whether the significant thinning has occurred in the inspected components or not. In the previous study, the authors presented an approximate estimation procedure as the first step for thickness measurement deviations at each inspected component and the statistical & quantitative characteristics of the measurement deviations using plant experience data. In this study, statistical significance was quantified for the current methods used for wall-thinning determination. Also, the authors proposed new estimation procedures for determining local wall-thinning to overcome the weakness of the current methods, in which the proposed procedure is based on analysis of variance (ANOVA) method using subgrouping of measured thinning values at all measurement grids. The new procedures were also quantified for their statistical significance. As the results, it is confirmed that the new methods have better estimation confidence than the methods having used until now.

• 소성∙가공
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• 제19권2호
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• pp.79-87
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• 2010

The Pipe bending process using high frequency local induction heating is an advanced technique to bend pipes with a small bending radius and a large diameter. Even though the pipe bending process is a quite widespread engineering practice, it depends heavily upon trial and error method by field engineers with several years of experience. So it is necessary to develop an integrated methodology for optimum design of the pipe bending process. During hot pipe bending using induction heating, outward wall thickness of a pipe is thinned due to tensile stress and the reduction of wall thickness is not allowed to exceed 12.5%. Taguchi method and dynamic reverse moment is proposed to maintain a reduction ratio of thickness within 12.5%, when D/t ratio is high. An application of the proposed approach was compared with those of the finite element analysis and has good in agreements.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(4)
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• pp.295-299
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• 1996

This analysis is to investigate the benefits and disadvantages of increasing the pressure tube wall thickness for CANDU reactor. Creep analysis of the pressure tube was performed for slightly enriched uranium (SEU) to establish the reduction in axial elogation and diametral creep provided by a thicker wall pressure tube.

• Journal of Welding and Joining
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• 제23권5호
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• pp.43-48
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• 2005

Conventional non-destructive techniques for inspection of the weld in pipelines require significant test time and high cost. Ultrasonic guided waves have been widely studied and successfully applied to various non-destructive tests with advantage of the long-range inspection. In this paper, a study on the application of ultrasonic guided waves to the long-range inspection of the pipeline is presented using a long-range guided wave inspection system, Wavemaker SE16, GUL. The characteristics and setup of the long-range guided wave inspection system and experimental results in pipes of with various diameter are introduced. The experimental results in mock-up pipes with cluster type detects show that the minimum detectable wall thickness reduction with this guided wave system is $2\~3\%$ in the pipe cross section area. And the wall thickness reduction of $5\%$ in cross section area can be detected when actual detection level is used. Therefore, the applicability of the guided wave systeme to long-range inspection of wall thickness reduction in pipes is verified.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.807-812
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• 2008

The various attempts is made to solve the energy and environment problems. In addition, people interested in their life quality want the more eco-friendly living space. So we suggested that the earth-sheltered house could be one of the eco-friendly and low energy consuming houses to meet the social interest. And we also made data for design of the earth-sheltered house to be applicable to climate of Korea. In this study, a simulation was performed to estimate a boundary temperature according to earth sheltering thickness at the earth-sheltered part(exterior wall) in the case of earth sheltering on the plane ground not using a sloped site. And we analyzed the reduction of a thermal load by using this boundary temperature. We also compared a case of earth sheltering at the vertical wall with a case of earth sheltering at the roof to know the thermal reduction effect of a case of earth sheltering at the vertical wall.

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.73-84
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• 1994

Using a model system that can compare the before and after of canal preparation in the same tooth, we measured the area of the cross section, and canal wall thickness of the distal portion of the mesial root of the mandibular molar, and compared the amount of reduction in the canal using hand flared preparation the Gates-Glidden drill flared preparation according to the changes in the MAF. The results were as follows. 1. After canal preparation, the canal wall thickness had no significant difference between the hand flared preparation and Gates-Glidden drill flared preparation. 2. The canal wall thickness, after canal preparation, there was no significant difference between the sizes of the MAF. 3. The area variation range of each cross section of root had no significant difference between MAF size and methods of canal preparation. 4. After canal preparation, the frequency of the canal wall thickness under 0.5mm showed 3.5mm below the furcation to be the most frequent with statistical significance(p<0.05). 2mm below the furcation and 5mm below the furcation followed but there was no statistical significance. 5. The danger zone of the mesial root of the mandibular molar seems to be around 3.5mm.

• 한국방사선학회논문지
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• 제12권3호
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• pp.373-379
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• 2018

본 논문에서는 척추측만증 환자의 진료를 위하여 필요한 Whole Spine Scanography 검사에서 촬영거리, 환자자세(전후 후전 방향), 흉부벽두께, 갈비뼈두께, 폐조직두께, 관전압, 고전압정류방식의 변화에 따른 유방의 입사선량의 차이에 대한 정량적인 자료를 제시하고자 하였다. 환자의 자세(전후방향과 후전방향)에 따른 유방 입사선량의 저감효과를 확인하기 위하여 관전압 90 kVp, 커마 0.1 mGy, 촬영거리 260 cm, 관전압의 리플율이 0인 인버터정류방식, 필터의 두께 3.5 mm, 환자의 흉벽의 두께 120 mm를 조건으로 Simulation of X-ray Spectra program을 이용하여 시뮬레이션 하였다. 그 결과 알루미늄 필터 두께 3.5 mm에서 2.6배, 흉벽의 두께 120 mm에서 25.7배, 고 관전압에서 1.43배, 관전압 리플율 0에서 1.14배의 선량 저감효과가 있었다. 각각의 입사 선량저감효과의 총합은 약 109배이었다. RANDO phantom의 자세(전후방향과 후전방향)에 따른 선량 저감효과를 확인하기 위하여 촬영거리 260 cm, 관전압 90 kVp, 관전류 270 mA, 촬영시간 0.31 sec, 관전압의 리플율이 0인 인버터정류방식, 필터의 두께 3.5 mm을 조건으로 측정한 결과 유방의 입사선량은 전후 방향에 비하여 후전방향이 평균 20.56배의 선량 저감효과가 있었다.