• Title/Summary/Keyword: Direct Current Potential Drop Method

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Statistical analysis of direct current potential drop data (직류전위차법 자료에 대한 통계적 자료분석)

  • Lee, Jeong-Hee;Lee, Woo-Dong
    • Journal of the Korean Data and Information Science Society
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    • v.21 no.1
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    • pp.139-146
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    • 2010
  • It was verified that the effect of the distance between current input point and output point on direct current potential drop (DCPD) in the material with two-dimensional surface notch. If the distance between potential drop measuring points was fixed at a certain distance, the potential drop was decreased with increasing the distance between current input and output points. DCPD technique was a useful method for surface crack sizing because the potential drop was proportional to the length of notch. In this paper, we suggest a statistical model to describe the data and want to find a significant variables to effect to potential drop. We use R program to analyze the data.

Evaluation of the Crack Initiation of Curved Compact Tension Specimens of a Zr-2.5Nb Pressure Tube Using the Unloading Compliance and Direct Current Potential Drop Methods (제하 컴플라이언스법 및 직류전위차법을 이용한 Zr-2.5Nb 압력관 휘어진 CT 시편의 균열시작 평가)

  • Jeong, Hyeon-Cheol;Ahn, Sang-Bok;Kim, Young-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.8 s.239
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    • pp.1118-1122
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    • 2005
  • The direct current potential drop (DCPD) method and the unloading compliance (UC) method with a crack opening displacement gauge were applied simultaneously to the Zr-2.5Nb curved compact tension (CCT) specimens to determine which of the two methods can precisely determine the crack initiation point and hence the crack length for evaluation of their fracture toughness. The DCPD method detected the crack initiation at a smaller load-line displacement compared to the UC method. As a verification, a direct observation of the fracture surfaces on the curved compact tension specimens was made on the CCT specimens experiencing either 0.8 to 1.0 mm load line displacement or various loads from $50\%\;to\;80\%$ of the maximum peak load, or $P_{max}$. The DCPD method is concluded to be more precise in determining the crack initiation and fracture toughness, J in Zr-2.5Nb CCT specimens than the UC method.

Pipe thinning model development for direct current potential drop data with machine learning approach

  • Ryu, Kyungha;Lee, Taehyun;Baek, Dong-cheon;Park, Jong-won
    • Nuclear Engineering and Technology
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    • v.52 no.4
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    • pp.784-790
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    • 2020
  • The accelerated corrosion by Flow Accelerated Corrosion (FAC) has caused unexpected rupture of piping, hindering the safety of nuclear power plants (NPPs) and sometimes causing personal injury. For the safety, it may be necessary to select some pipes in terms of condition monitoring and to measure the change in thickness of pipes in real time. Direct current potential drop (DCPD) method has advantages in on-line monitoring of pipe wall thinning. However, it has a disadvantage in that it is difficult to quantify thinning due to various thinning shapes and thus there is a limitation in application. The machine learning approach has advantages in that it can be easily applied because the machine can learn the signals of various thinning shapes and can identify the thinning using these. In this paper, finite element analysis (FEA) was performed by applying direct current to a carbon steel pipe and measuring the potential drop. The fundamental machine learning was carried out and the piping thinning model was developed. In this process, the features of DCPD to thinning were proposed.

The Influence of Distance between Current Supply Points on Potential Drop in DCPD (직류전위차법에서 전류 입출력점 사이 거리가 전위차에 미치는 영향)

  • Lee, Jeong-Hee
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.2
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    • pp.104-107
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    • 2009
  • It was verified that the effect of the distance between current input point and output point on direct current potential drop(DCPD) in the material with two-dimensional surface notch. If the distance between potential drop measuring points was fixed at a certain distance, the potential drop was decreased with increasing the distance between current input and output points. Hence it is the effect way to increase sensitivity in DCPD that the current input and output points should be located near the potential measuring points. DCPD was a useful method for surface crack sizing because the potential drop was proportional to the length of notch. When the current input and output points are located near the potential measuring points, even small length crack can be measured by DCPD technique.

Calculation of the Crack Length for a Pipe Specimen using the Modified Load Ratio Method (수정된 하중비법을 이용한 배관 시험편의 균열 길이 계산)

  • Choi, Jung-Hun;Huh, Yong;Koo, Jae-Mean;Seok, Chang-Sung;Park, Jae-Sil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.12
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    • pp.1375-1382
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    • 2009
  • The objective of this paper is to apply the load ratio method to the measurement of the crack length of the real scale pipe specimen. The load ratio method was modified and finite element analyses were performed to derive the relationship between the normalized compliance and the normalized crack length for the pipe specimen. In order to measure the crack length, the direct current potential drop method and the modified load ratio method were applied to the pipe test. The applicability of the modified load ratio method was confirmed by comparing the calculated crack length with the measured crack length from the pipe experiment.

Verification of the Viability of Equipotential Switching Direct Current Potential Drop Method for Piping Wall Loss Monitoring with Signal Sensitivity Analysis (등전위 교번식 직류전위차법의 신호 정밀도 검증을 통한 배관 감육 진단 기술에의 적용성 검증)

  • Ryu, Kyung-Ha;Hwang, Il-Soon;Kim, Ji-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.2
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    • pp.191-198
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    • 2008
  • Flow accelerated corrosion (FAC) phenomenon of low alloy carbon steels in nuclear power plant has been known as one of major degradation mechanisms. It has a potential to cause nuclear pipe rupture accident which may directly impact on the plant reliability and safety. Recently, the equipotential switching direct current potential drop (ES-DCPD) method has been developed, by the present authors, as a method to monitor wall loss in a piping. This method can rapidly monitor the thinning of piping, utilizing either the wide range monitoring (WiRM) or the narrow range monitoring (NaRM) technique. WiRM is a method to monitor wide range of straight piping, whereas NaRM focuses significantly on a narrow range such as an elbow. WiRM and NaRM can improve the reliability of the current FAC screening method that is based on computer modeling on fluid flow conditions. In this paper, the measurements by ES-DCPD are performed with signal sensitivity analyses in the laboratory environment for extended period and showed the viability of ES-DCPD for real plant applications.

Study on Localized Corrosion Cracking of Alloy 600 using EN-DCPD Technique (EN-DCPD 방법을 이용한 Alloy 600 재료의 국부부식균열 연구)

  • Lee, Yeon-Ju;Kim, Sung-Woo;Kim, Hong-Pyo;Hwang, Seong-Sik
    • Corrosion Science and Technology
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    • v.12 no.2
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    • pp.93-101
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    • 2013
  • The object of this work is to establish an electrochemical noise(EN) measurement technique combined with a direct current potential drop(DCPD) method for monitoring of localized corrosion cracking of nickel-based alloy, and to analyze its mechanism. The electrochemical current and potential noises were measured under various conditions of applied stress to a compact tension specimen in a simulated primary water chemistry of a pressurized water reactor. The amplitude and frequency of the EN signals were evaluated in both time and frequency domains based on a shot noise theory, and then quantitatively analyzed using statistical Weibull distribution function. From the spectral analysis, the effect of the current application in DCPD was found to be effectively excluded from the EN signals generated from the localized corrosion cracking. With the aid of a microstructural analysis, the relationship between EN signals and the localized corrosion cracking mechanism was investigated by comparing the shape parameter of Weibull distribution of a mean time-to-failure.

Dynamic Fracture Testing of Welding part of Nuclear Piping by Using Normalization Method (정규화법을 이용한 원전배관 용접부의 동하중 파괴저항시험)

  • Huh, Yong;Cho, Sung-Keun;Park, Jae-Sil;Seok, Chang-Sung
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.262-267
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    • 2004
  • The unloading compliance method is the most commonly used method to evaluate the fracture resistance characteristics of a material. In dynamic loading condition, the direct current potential drop(DCPD) method has been used because the unloading compliance method can not be applied due to the discontinuity of loading. However, even in the dynamic test using DCPD method, there is a problem that the voltage drops sharply on the initiation of crack. For the reason metioned above, the normalization method was suggested on ASTM E 1820 which is revised recently, as a new method to evaluate the dynamic fracture resistance characteristic. The nomalization method can be used to obtain a fracture resistance curve directly from a load-load line displacement. In this study, we obtained two fracture resistance curves from static test of welding part of nuclear piping both by unloading compliance and nomalization method. The two curves were almost same each other, so the adaptability of the nomalization method has been proved. We conducted a dynamic fracture resistance test for the same material. The fracture resistance curve from the dynamic test was obtained by normalization method and compared to that of the static test result.

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Studies on effects of calibration methods and current lead position on the direct current potential drop method for crack length measurement (직류전압강하법에 의한 균열길이 측정에 미치는 도선의 위치 및 보정방법의 영향에 관한 연구)

  • Cho, C.C.;Kim, I.S.;Kim, S.S.;Choe, S.J.;Hur, B.Y.
    • Analytical Science and Technology
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    • v.10 no.4
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    • pp.300-306
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    • 1997
  • The effective resolution of the direct current potential drop (DCPD) method for crack length determination is strongly affected by a number of factors including wire locations and calibration method. In the present study, the effects of wire locations, thermal EMF and reference probe locations on the accuracy of calibration methods, including Hicks-Pickard equation and Johnson's equation, were examined with the CT specimens which were nine times larger than the standard specimen. In light of experimental results, it was found that Hicks-Pickard equation can accurately represent the a/W-V/Vo relationship when current input wire is located at the load line. It was also found that the accuracy of DCPD method can be greatly improved with the thermal EMF calibration and the use of Vo value at a/W = 0.241. The use of reference potential was found to be impractical when current input wire is located at the load line.

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