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USC 발전소용 12 Cr 계 마르텐사이트강의 저주기피로특성
김국철(Kim Kuk-Cheol),석진익(Suk Jin-Ik),김병훈(Kim Byung-Hoon),김정태(Kim Jeong-Tae) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The objective of this study is to investigate the characteristics of low cycle fatigue for the candidate bucket material (DS2B2) developed by Doosan. Turbine bucket is subjected to the repeated thermal stress during shutdown and heat-up. Therefore, LCF characteristics is of much concern in order to meet the fatigue life requirement. At room and service temperature of 593℃, LCF test were carried out for DS2B2 and commercial materials COST B2. Both DS2B2 and COST B2 materials were refined by VIM and ESR process. DS2B2 material was more superior to COST B2 for LCF life. The LCF characteristics of DS2B2 materials manufactured by VIM and ESR processes was improved as compared with that by VIM process. It can be seen that the harmful element S and non-metallic inclusions were reduced and the grain size was finer through the ESR refining process.
22Cr-9Mo-3Fe-4Nb 니켈기 초내열합금의 저주기 피로에 따른 미세조직변화
송영석 ( Youngseok Song ),석진익 ( Jinik Suk ),강정윤 ( Chung Yun Kang ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.9
Abstract: A new Ni based superalloy with high fatigue resistance and fine grain was considered as a material for high-pressure buckets in fossil fuel power plants. Since such buckets are usually exposed to extreme operating conditions, low cycle fatigue tests were conducted to understand the microstructure evolution of the material during cyclic fatigue under total strains of 0.8, 0.9, 1.0 and 1.2%, and temperatures of 566, 593, 621, 649 and 700 ℃. Microstructural analysis of fractured specimens was conducted using TEM, SEM and OM to observe changes in the γ″ morphology, carbides, and fracture mode. Based on the observations of microstructural changes and low cycle fatigue properties, it can be concluded that grain size had the dominant effect on low cycle fatigue properties, regardless of the size of the transformed carbides and precipitates in these alloy systems. (Received March 7, 2017; Accepted June 7, 2017)
김국철(K.C. Kim),석진익(J.I. Suk) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
A stochastic evaluation of fatigue crack growth in turbine rotor materials is important to enhance the reliability in the integrity analysis of power generation plants. In order to evaluate the scatter of fatigue crack growth length, experimental tests on fatigue crack propagation are carried out at a constant load amplitude using CrMoV turbine rotor steel, and 14 compact tension specimens are tested at the condition of maximum load 10.5 kN, stress ratio 0.1, and 10 ㎐ frequency at room temperature. The crack length is measured at size intervals of 0.2 ㎜ in crack growth, using the compliance method. We observed experimentally that the crack growth rate was strongly dependent upon the previous rate at each cyclic loading. Crack growth length is separated into two parts: previous crack growth rate-dependent length and variation-dependent length. A weight function is introduced for exact analysis. The previous crack growth rate-dependent length is then expressed as a function of two or three terms. The results are compared and evaluated for better prediction.
김국철(K.C. Kim),석진익(J.I. Suk),권희경(H.K. Kwon) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.11
A spent nuclear fuel cask should safe in the case of most severe accident loading during transportation. Therefore, in order to verify the integrity of the shipping cask manufactured by doosan heavy industries for the first time in Korea, rapid loading K1C tests has performed as material property evaluation. In this paper, the dynamic fracture toughness obtained by rapid loading K<SUB>IC</SUB> tests is discussed. The procedure of the integrity evaluation of the shipping cask is as follow: First, the maximum flaw size for the full area of forging product of the shipping cask is measured by nondestructive examination. Second, the dynamic fracture toughness test is carried out at -40℃. Third, FEM is performed for the model of the shipping cask with the maximum size flaw measured by NDE under seismic loading. Finally, the integrity of the shipping cask is evaluated by comparing maximum stress intensity factor calculated by FEM with dynamic fracture toughness measured by the experiment. In the integrity evaluation, our company has carried out nondestructive examination and dynamic fracture toughness test, and GNB Company in Germany has carried out FEM analysis. From the evaluation, the integrity of shipping cask was confirmed.
초초임계압 발전용 소재의 장시간 열처리에 따른 미세조직 변화와 기계적 특성의 상관관계 연구
주성욱,유정훈,신기삼,허성강,이재현,석진익,김정태,김병훈,Joo Sungwook,Yoo Junghoon,Shin Keesam,Hur Sung Kang,Lee Je-Hyun,Suk Jin Ik,Kim Jeong Tae,Kim Byung Hoon 한국재료학회 2005 한국재료학회지 Vol.15 No.1
For the good combination of high-temperature strength, toughness and creep property, $9-12\%$ chromium steels are often used for gas turbine compressors, steam turbine rotors, blade and casing. In this study, the correlation of microstructural evolution and mechanical properties was investigated fur the specimens heat-treated at 600, 650 and $700^{\circ}C$ for 1000, 3000 and 5000 hrs. The microstructure of as-received specimen was tempered martensite with a high dislocation density, small sub-grains and fine secondary phase such as $M_23C_6$. Aging for long-time at high temperature caused the growth of martensite lath and the decrease of dislocation density resulting in the decrease in strength. However, the evolution of secondary phases had influence on hardness, yield strength and impact property. In the group A specimen aged at $600^{\circ}C\;and\;650^{\circ}C$, Laves phase was observed. The Laves phase caused the increase of the hardness and the decrease of the impact property. In addition, the abrupt growth of secondary phases caused decrease of the impact property in both A and B group specimens.
안성종(Sung-Jong Ahn),박누가(Luke Park),윤태준(Tae-Jun Yun),석진익(Jin-ik Suk) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.4
Doosan has been developing a 5MW class gas turbine engine, DGT-5. Campbell diagram has been used for prediction of possible occurrence of resonances of rotating machinery. The Campbell diagram consists of blade natural frequency and excitation frequency. In this paper, modal characteristics of compressor and turbine blades are investigated and Campbell diagram is obtained. We calculated compressor and turbine blade’s natural frequency using ANSYS tool. The result has been verified through test.
5패드 틸팅 패드 베어링의 설계 조건 변화가 소형 가스터빈의 횡진동 특성에 미치는 영향
하진웅(Ha, Jin-Woong),명지호(Myung, Ji-Ho),석진익(Suk, Jhin-Ik),이안성(Lee, An-Sung),김영철(Kim, Young-Cheol) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.8
In tilting pad bearing design process, the selection of the proper configuration type of either a load-between-pad(LBP) or load-on-pad(LOP) as well as preload and pivot offset conditions is to be carefully considered. Also the bearing needs to be designed in order to be suited for the rotor-bearing system and operating condition. In this paper, it is observed that the dynamic characteristics in a five pad tilting pad bearing for the LBP and the LOP configurations are influenced by the variation of preload and pivot offset. In this context, rotor dynamic analysis of the 5 MW industrial gas turbine supported by the tilting pad bearing at the front and roller bearing at the rear is carried out based on the dynamic coefficients of the tilting pad bearing investigated. The result shows that two rigid body critical modes experience various changes according to the influence of the tilting pad bearing uniquely applied to one side of this machine. Mainly, the second critical speed, the rigid body mode of conical shape with high whirling in the tilting pad bearing, is significantly changed by preload and pivot offset regardless of the LBP and LOP configurations. And, the first critical mode, the rigid body mode of conical shape with high whirling in the roller bearing, is sensitively affected by preload applied to the LOP configuration and by its asymmetric dynamic properties.