• Title/Summary/Keyword: Degradation test

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A study on the evaluation for material degradation of 0.0Cr-0.5Mo steel by a electrochemical polarization method (전기화학적 분극법에 의한 1.0Cr-0.5Mo강의 경년열화 평가에 관한 연구)

  • Na, Eui-Gyun;Kim, Hoon;Lee, Jong-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.1
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    • pp.177-189
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    • 1998
  • The contents of this paper include a non-destructive technique for evaluating the degradation of the boiler superheater tube in a fossil power plant through an electrochemical polarization test. Correlation between Ip of polarization parameter and SP-DBTT for the superheater tubes in long-term use was obtained. 1.0Cr-0.5Mo steel was degraded by softening, and the degree of degradation was dependent upon carbides with Cr and Mo elements. Since brittle fracture at low temperature and ductile fracture mode at high temperature were shown, similarity between standard Charpy and small punch tests could be found. In addition, SP-DBTT showing the degree of degradation was higher, as the time-in use of the materials got longer. Electrolyte including picric acid of 1.3 g in distilled water of 100ml at 25.deg. C temperature and sodium tridecylbenzene sulfonate with 1g could be applied to evaluate the degradation of 1.0Cr-0.5Mo steel by means of the electrochemical polarization test. Ip and Ipa values measured through the electrochemical test are the appropriate parameters for representing the degradation of the superheater tube(1.0Cr-0.5Mo steel) for the fossil power plant. It is poassible to evaluate the degradation of materials with different time histories electrochemically, by Ip value only, at field test.

A study on the developing the diagnosis technology and expert system in fossil power plant (화력발전설비 진단기술 및 전문가 시스템개발에 관한 연구)

  • Baik, Young-Min;Jeong, Hee-Don;Shin, Eun-Ju
    • Proceedings of the SAREK Conference
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    • 2008.11a
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    • pp.642-648
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    • 2008
  • In order to analyze the causes of fossil power plant facilities due to a degradation and corrosion, artificial degraded materials composed of the facilities were manufactured. Various experiment were performed based on mechanical test, microstructure observation, hardness test, electrochemical potentiokinetic reactivation test(EPR) and corrosion scale thickness measurement test. The master curves were write out using Larson-Miller parameter to evaluate the degree of degradation with the above diagnosis methods. These data were applied to materials database of fossil power plant diagnosis. Finally expert system on the fossil power plant diagnosis was developed using the master curves and diagnosis algorithms.

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Evaluation of the Degradation Trend of the Polyurethane Resilient Pad in the Rail Fastening System by Multi-stress Accelerated Degradation Test (복합가속열화시험을 통한 레일체결장치 폴리우레탄 탄성패드의 열화 경향 분석)

  • Sung, Deok-Yong;Park, Kwang-Hwa
    • Journal of the Korean Society for Railway
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    • v.16 no.6
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    • pp.466-472
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    • 2013
  • The use of a concrete track is gradually growing in urban and high-speed railways in many part of the world. The resilient pad, which is essentially when concrete tracks are used, plays the important role of relieving the impact caused by train loads. The simple fatigue test[1] to estimate the variable stiffness of resilient pads is usually performed, but it differs depending on the practical conditions of different railways. In this study, the static stiffness levels of used resilient pads according to passing tonnages levels were measured in laboratory tests. Also, the simple fatigue test and the multi-stress accelerated degradation test for new resilient pads were performed in a laboratory. The static stiffness of the used pad was compared with the results of tests of usage times and cycles. The results of the comparison showed that the variable static stiffness levels of the used pad were similar to results of the multi-stress accelerated degradation test considering the fatigue and heat load. With a T-NT equation related to the degree of the multi-stress accelerated degradation, a model of multi-stress accelerated degradation for a resilient pad was devised. It was found through this effort that the total acceleration factor was approximately 2.62. Finally, this study proposes an equation for a multi-stress accelerated degradation model for polyurethane resilient pads.

Study on stiffness deterioration in steel-concrete composite beams under fatigue loading

  • Wang, Bing;Huang, Qiao;Liu, Xiaoling;Ding, Yong
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.499-509
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    • 2020
  • The purpose of this paper is to investigate the degradation law of stiffness of steel-concrete composite beams after certain fatigue loads. First, six test beams with stud connectors were designed and fabricated for static and fatigue tests. The resultant failure modes under different fatigue loading cycles were compared. And an analysis was performed for the variations in the load-deflection curves, residual deflections and relative slips of the composite beams during fatigue loading. Then, the correlations among the stiffness degradation of each test beam, the residual deflection and relative slip growth during the fatigue test were investigated, in order to clarify the primary reasons for the stiffness degradation of the composite beams. Finally, based on the stiffness degradation function under fatigue loading, a calculation model for the residual stiffness of composite beams in response to fatigue loading cycles was established by parameter fitting. The results show that the stiffness of composite beams undergoes irreversible degradation under fatigue loading. And stiffness degradation is associated with the macrobehavior of material fatigue damage and shear connection degradation. In addition, the stiffness degradation of the composite beams exhibit S-shaped monotonic decreasing trends with fatigue cycles. The general agreement between the calculation model and experiment shows good applicability of the proposed model for specific beam size and fatigue load parameters. Moreover, the research results provide a method for establishing a stiffness degradation model for composite beams after fatigue loading.

Reliability Analysis of Degradation Data for LEDs (LED 열화데이터의 신뢰성 분석)

  • Park, Chang-Kyu
    • Journal of Applied Reliability
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    • v.9 no.1
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    • pp.59-69
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    • 2009
  • LEDs have rapidly replaced old light devices such as incandescent or fluorescent lamps, and have been widely applied in general lighting, signals, automobile, signs and others. Since LEDs are for both indoor and outdoor use, temperature and humidity inevitably affect its reliability. We explain the result of the degradation life test on LEDs, and guide to reliability analysis procedure. Analysis on reliability measures are performed by Weibull++6 program, and a common shape parameter of Weibull distribution on the LED is suggested. Also, we make a description of reliability analysis procedures for the degradation data using collected test data from degradation tests. Reliability analysis procedures are consisted of estimating degradation models and failure time, verifying of distribution and parameters of the distribution, and estimating of reliability measures. Finally, this paper suggests reliability analysis method for light characteristics on LEDs.

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A Study on the Degradation Characteristics of ZnO Ceramic Devices by the Valence Controls (원자가 제어에 의한 ZnO 세라믹 소자의 열화특성 연구)

  • 소순진;김영진;소병문;박춘배
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.157-160
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    • 2001
  • Three sets of ZnO ceramic devices (reference samples with Matsuoka\`s composition; added 7o MgO, A1$_2$O$_3$, SiO$_2$) have been prepared by the conventional mixed oxide route. These additives were determined by the factors of valences and ionic radiuses. DC accelerated degradation test was performed for analysis of degradation characteristics versus the various additives. The conditions of DC degradation test were 115${\pm}$2$^{\circ}C$ for 12h. Using XRD and SEM, the Phase and microstructure of samples were analyzed respectively. E-J analysis was used to determine ${\alpha}$. Frequency analysis was accomplished to understand the relationship between R$\sub$g/ and $R_{b}$ with the electric stress at the equivalent circuit.

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LED 칩 열화특성에 적합한 열화모델 기반의 수명예측 시스템 구현

  • Yu, Gi-Hun;Lee, Jae-Hun;Kim, Dal-Seok;Lee, Mu-Seok;Yun, Yang-Gi;Han, Ji-Hun;Jang, Jung-Sun
    • Proceedings of the Korean Reliability Society Conference
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    • 2011.06a
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    • pp.79-85
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    • 2011
  • LED(Light Emitting Diode) is a powerful device used in applications as diverse as replacements for aviation lighting, automotive lighting as well as in traffic signals. This study is to propose a prediction system based on the degradation model of LED which is determined by combining scale and shape parameter. The degradation model is analysed goodness of fit test using calculated R-square, and is compared with previous models. A LED prediction system using degradation model is developed to automate estimations of degradation parameters and lifetimes.

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A Study on the Corrosion and Degradation of Boiler Tubes Steel in Fossil Power Plant

  • Baik, Young Min;Jeong, Hee Don;Kweon, Young Gak
    • Corrosion Science and Technology
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    • v.5 no.4
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    • pp.123-128
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    • 2006
  • It was analyzed the causes of boiler tube rupture due to a degradation and corrosion on the boiler tubes in fossil power plant. The experiments were carried out among samples taken from the operating facilities. The result were analyzed based on experimental results from mechanical strength, microstructure observation, and hardness measurement in order to determine the cause of local rupture on boiler tubes. In general, 2.25Cr-1Mo steel generates carbides, it is coarsened, its ductility and strength abruptly decreased as degradation is in progress, In order to confirm this phenomenon, we observed changes of the mount of Cr and Mo of carbide by carrying out EDX chemical composition analysis. The amount of Cr and Mo in the degraded material or service exposed material gradually increased the amount of Mo but initially they were almost maintained at the same amount. Furthermore, we observed that the carbide become coarsened both in the grain and at the grain boundary. Tensile test was carried out to measure a material hardness and to recognize a drop-off of hardness. Overall result for tensile strength and hardness turned out to be lower than new material and mechanical strength and hardness was degraded as the material degradation was in progress.

A Study on the 43$0^{\circ}C$ Degradation Behavior of Cast Stainless Steel(CF8M)(I);Evaluation of Degradation mechanism, Static and Fatigue Strength (주조 스테인리스강 CF8M의 43$0^{\circ}C$ 열화거동에 관한 연구(I);열화기구.정적 및 피로강도평가)

  • Gwon, Jae-Do;Park, Jung-Cheol;Lee, Yong-Seon;Lee, U-Ho;Park, Yun-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.8 s.179
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    • pp.1910-1916
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    • 2000
  • The five classes of the thermally aged CF8M specimen are prepared using an artificially accelerated aging method. Namely, after the specimens are held for 100, 300, 900, 1800, and 3600hrs at 430$^{\circ}C$ respectively, the specimens are water-cooled to room temperature. The impact energy variations are measures for both the aged and virgin specimens through the Charpy impact tests in addition to the microstructure observation, tensile, hardness and fatigue crack growth tests. From the present investigation the following results are obtained : 1) The difference among the thermally degraded specimens can be distinguished through their microstructures, 2) Hardness and tensile strength are increased to 300hrs, degradation specimen, while elongation and reduction area are decreased to 3600hrs degradation specimen, and impact energy is decreased to 1800hrs degradation specimen, 3) The FCG rates for thermally degraded specimens are larger than that of the virgin specimen.

Seismic behavior of simplified electrical cabinet model considering cast-in-place anchor in uncracked and cracked concretes

  • Bub-Gyu Jeon;Sung-Wan Kim;Sung-Jin Chang;Dong-Uk Park;Hong-Pyo Lee
    • Nuclear Engineering and Technology
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    • v.55 no.11
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    • pp.4252-4265
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    • 2023
  • In the case of nuclear power plants near end of their design life, a reassessment of the performance of safetyrelated equipment may be necessary to determine whether to shut down or extend the operation of the power plant. Therefore, it is necessary to evaluate the level of performance decline due to degradation. Electrical cabinets, including MCC and switchgear, are representative safety-related equipment. Several studies have assessed the degradation and seismic performance of nuclear power plant equipment. Most of those researches are limited to individual components due to the size of safety-related equipment and test equipment. However, only a few studies assessed the degradation performance of electrical cabinets. The equipment of various nuclear power plants is anchored to concrete foundations, and crack in concrete foundations is one of the most representative of degradation that could be visually confirmed. However, it is difficult to find a study for analysis through testing the effect of cracks in concrete foundations on the response of electrical cabinet internal equipment fixed by anchors. In this study, using a simple cabinet model considering cast-in-place anchor in uncracked and cracked concretes, a tri-axial shaking table tests were performed and the seismic behavior were observed.