• 사물인터넷융복합논문지
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• 제8권5호
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• pp.11-16
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• 2022

상수도분야 인공지능 기술개발 관심도가 증가함에 따라 상수도 관로에 대해서 노후관 상태평가 데이터 결과를 활용하여 반복적인 학습으로 개량 의사결정 등급을 예측할 수 있는 인공신경망 알고리즘을 개발하고 검증과정을 통하여 가장 신뢰성 있는 예측 모델을 제시하고자 한다. 2020년 한강유역의 노후관로 정비 기본계획에 의한 간접평가 데이터 12개 항목을 기반으로 데이터 전처리 하고 인공신경망 알고리즘을 적용하여 반복학습과 검증을 통해 계산된 결과값과 직접평가 결과값의 일치율이 90% 이상이 되도록 역전파 과정을 통해 가중치를 업데이트 하면서 최적화하여 관로 등급을 예측하는 알고리즘을 개발하였다. 알고리즘 정확도 검증결과 모든 관종 데이터가 고르게 분포되어 있고 학습 데이터가 많아야 예측평가 정확도가 높아지는 것을 확인할 수 있었다. 향후 전국의 다양한 데이터가 확보되면 인공신경망을 이용한 관로등급 예측의 신뢰도가 좀 더 향상되어 객관화된 노후관 상태평가 의사결정 지원 역할을 수행할 수 있을 것으로 기대된다.

• Smart Structures and Systems
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• 제7권4호
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• pp.241-262
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• 2011

Cast iron pipe has been used as a water distribution technology in North America since the early nineteenth century. The first cast iron pipes were made of grey cast iron which was succeeded by ductile iron as a pipe material in the 1940s. These different iron alloys have significantly different microstructures which give rise to distinct mechanical properties. Insight into the non-destructive structural condition assessment of aging pipes can be advantageous in developing mitigation strategies for pipe failures. This paper examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. The experimental program included microstructure evaluation and ultrasonic, tensile, and flexural testing. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference); the ductile iron pipes showed the smaller variation in wave velocities. Thus, the variation of elastic properties for ductile iron was not enough to define a linear correlation because all the measurements were practically concentrated in single cluster of points. The cross-sectional areas of the specimens tested varied as a result of minor manufacturing defects and levels of corrosion. These variations affect the large strain testing results; but, surface defects have limited effect on wave velocities and may also contribute to the low correlations observed. Lamb waves are typically not considered in the evaluation of ultrasonic pulse velocity. However, Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using specimens manufactured in the laboratory must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes.

• 한국지반환경공학회 논문집
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• 제22권11호
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• pp.15-21
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• 2021

도심지 지하에 매설된 열수송관 등 지하매설관이 점차 노후화함에 따라 파손에 의한 인적, 경제적 피해가 증가하고 있다. 외부로 노출되지 않아 파손 등 문제점을 즉시 확인하기 어려운 열수송관의 특징을 고려할 때, 시설물 유지관리를 통해 주기적으로 수집하는 이력정보를 기반으로 시설물의 상태를 간접적으로 확인하는 방법이 현실적이다. 본 논문에서는 열수송관 이력정보를 검토하여 파손확률과 연관성을 가지는 평가인자를 도출하고, 이를 통해 파손확률을 추정하는 방법론을 제시하고자 한다. 파손확률 추정을 위한 영향인자는 유럽의 사례, 국내 열수송관 관리기준 등을 분석해 도출하였으며, 데이터의 확보 가능성도 함께 고려하여 선정하였다. 열수송관 설치기준이 변경된 1999년을 기준으로 매설시기에 따라 2가지 파손확률 추정 함수를 달리 제시하고 관경, 용도, 관리주체 등 평가인자별 정보에 따른 가중치를 부여하여 파손확률을 보정하여 파손확률추정의 신뢰성을 확보하였다.

• 전기학회논문지
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• 제59권6호
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• pp.1087-1094
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• 2010

We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.

• 한국재료학회지
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• 제19권12호
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• pp.692-698
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• 2009

Inconel 718 alloy has excellent mechanical properties at room temperature, high temperature and cryogenic conditions. UTS of base metal is about 900MPa at room temperature; this is increased up to 1300MPa after heat treatment & aging-hardening. Mechanical properties of Inconel 718 Alloy were similar to those shown in the the results for tensile test; mechanical properties of Inconel 718 alloy's GTAW were similar to those of base metal's properties at room temperature. Mechanical properties at cryogenic conditions were better than those at room temperature. Heat-treated Inconel 718, non- filler metal GTAW on Inconel 718 and GTAW used filler metal on Inconel 718's UTS was 1400MPa at cryogenic condition. As a result, the excellent mechanical properties of Inconel 718 alloy under cryogenic conditions was proved through tensile tests under cryogenic conditions. In addition, weldability of Inconel 718 alloy under cryogenic conditions was superior to that of its base-metal. In this case, UTS of hybrid joint (IS-G) at -100$^{\circ}C$ was 900MPa. Consequently, UTS of Inconel 718 alloy is estimated to increase from -100$^{\circ}C$ to a specific temperature below -100$^{\circ}C$. Therefore, Inconel 718 alloy is considered a pertinent material for the production of Lox Pipe under cryogenic conditions.