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Method for Predicting Thermal Fatigue Life of Thermal Barrier Coatings Using TGO Interface Stress
Junghan Yun,Sunguk Wee,Soo Park,Jeong-Min Lee,Hyunwoo Song,Chang-Sung Seok 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.9
Thermal barrier coatings (TBCs) applied to high-temperature components of gas turbines consist of a ceramic top coat, a metallic bond coat, and thermally grown oxide (TGO) generated between the top coat and bond coat. Because TBCs are subjected to repeated thermal stress at the coating interface under thermal fatigue conditions and eventually breakage, it is crucial to evaluate the thermal fatigue durability of TBCs according to the stress. In this study, coin-type TBC specimens were prepared by depositing commercial coating powders on Ni-based super alloys via the air plasma spray method, and the thermal fatigue life of the TBCs was experimentally evaluated. According to the test results and references, a finite-element analysis was conducted. The maximum stress of the TGO interface was evaluated according to the thickness and equivalent elastic modulus, and simulating the microstructure including the pores of the top coat. Using these relationships, a thermal fatigue life prediction equation considering the coating thickness (t), equivalent elastic modulus (E), and operating temperature (T) was derived, and subsequently verified.
윤정한(Junghan Yun),이정민(Jeong-Min Lee),석창성(Chang-Sung Seok),권석환(Sukhwan Kwon),윤병관(Byoungkwan Yun),장병문(Byungmoon Chang) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.1
Gas turbine, the core equipment of the power plant, is capable of rapid starting operation and has less carbon dioxide emission than coal power plant. So it has the advantage of being eco- friendly. In order to increase the efficiency of these gas turbines, the turbine inlet temperature has steadily increased and to ensure the safety of the gas turbine, means for protecting parts exposed to high temperatures have also been developed. Protective coating technology is one of them, which plays the role of lowering the temperature of the base metal and preventing oxidation and corrosion. In this paper, thermal fatigue test simulating the operation environment was conducted using the Amdry 9951 protective coating powder applied to the HPT Heat Shield for the Alstom GT 24 gas turbine and the performance before and after the thermal fatigue test was evaluated and examined by adhesive strength test and SEM (EDS) analysis.
Yun, Yeo-Min,Song, Junghan,Ji, Misuk,Kim, Jeong-Ho,Kim, Yongkang,Park, Taesung,Song, Sang Hoon,Park, Seungman,Kim, Min Jin,Nho, Sun Jin,Oh, Kyung Won The Korean Society for Laboratory Medicine 2017 Annals of Laboratory Medicine Vol.37 No.1
<P><B>Background</B></P><P>For correct interpretation of the high-density lipoprotein cholesterol (HDL-C) data from the Korea National Health and Nutrition Examination Survey (KNHANES), the values should be comparable to reference values. We aimed to suggest a way to calibrate KNHANES HDL-C data from 2008 to 2015 to the Centers for Disease Control and Prevention (CDC) reference method values.</P><P><B>Methods</B></P><P>We derived three calibration equations based on comparisons between the HDL-C values of the KNHANES laboratory and the CDC reference method values in 2009, 2012, and 2015 using commutable frozen serum samples. The selection of calibration equation for correcting KNHANES HDL-C in each year was determined by the accuracy-based external quality assurance results of the KNHANES laboratory.</P><P><B>Results</B></P><P>Significant positive biases of HDL-C values were observed in all years (2.85-9.40%). We created the following calibration equations: standard HDL-C=0.872×[original KNHANES HDL-C]+2.460 for 2008, 2009, and 2010; standard HDL-C=0.952×[original KNHANES HDL-C]+1.096 for 2012, 2013, and 2014; and standard HDL-C=1.01×[original KNHANES HDL-C]-3.172 for 2011 and 2015. We calibrated the biases of KNHANES HDL-C data using the calibration equations.</P><P><B>Conclusions</B></P><P>Since the KNHANES HDL-C values (2008-2015) showed substantial positive biases compared with the CDC reference method values, we suggested using calibration equations to correct KNHANES data from these years. Since the necessity for correcting the biases depends on the characteristics of research topics, each researcher should determine whether to calibrate KNHANES HDL-C data or not for each study.</P>
Variation Analysis of DC Characteristics for Multi-Finger MOSFETs
Chulhyun Park,Junghan Kang,Seong-Ook Jung,Ilgu Yun 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
Variation analysis of the DC characteristics for multi-finger MOSFETs is investigated using the measured data from the test structure. The DC characteristics of multi-finger MOSFET, such as the threshold voltage, saturation current, saturation voltage and unit-finger current are analyzed according to the finger length and the number of fingers. The analysis results show which design factor can impact on the DC characteristics of multi-finger MOSFET and provide the more accurate prediction for the operation of multi-finger MOSFET.
Kang, Giseok,Yun, Joho,Cho, Jin‐,Seong,Yoon, JungHan,Lee, Jong‐,Hyun WILEY‐VCH Verlag 2016 Electroanalysis Vol.28 No.4
<P><B>Abstract</B></P><P>This work presents a novel micro electrical impedance spectroscopy (μEIS) technique that can measure and discriminate the electrical signal responses of biotissues in real time. An EoN (EIS‐on‐a‐needle), EIS on the surface of a fine needle (400 μm in diameter), was fabricated using a newly developed flexible photomask film. The base material of the photomask is parylene‐C, which allows uniform contact on the curved surface of the needle; thus, the designed electrode patterns of the photomask can be transferred onto the needle surface with a high resolution (2.95 % or less in dimensional error). To validate the developed EoN as an electrical sensor, ex vivo experiments with various biotissues—butchered pork (skin, fat, and muscle) and human breast tissues (normal and cancerous)—were conducted by measuring real‐time electrical impedance during a frequency sweep. The conductivities (relative permittivity) of the pork tissues were evaluated by electrical equivalent circuit analysis: 56.6 mS/m (37,800), 68.0 mS/m (74,755), and 74.9 mS/m (26,145) for the skin, fat, and muscle, respectively. Moreover, the normal and cancerous tissues were well distinguished by electrical resistance at 4.04 kHz for various cancer grades (Elston grades 1, 2, and 3). Analysis of the electrical impedance suggests that the EoN can be utilized to diagnose the physiological states of biotissues in clinical use.</P>