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권재도,문윤배,김상태,Kwon, Jae-Do,Moon, Yun-Bae,Kim, Sang-Tae 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1
In order to develop the evaluation methods of degradation for the Ni-Cr-Mo-V steel, which is in use for turbine rotor in nuclear power plant, the degraded materials were prepared by simulated degradation methods. The result of impact test and fatigue crack growth test shows that the FATT(Fracture Appearance Transition Temperature) and fatigue crack growth rate increased with the increase of degradation. And the result of new electrochemical polarization test method was suggested for the evaluating FATT, fatigue crack growth exponent and coefficient C values based on the results of relationship between corrosion current density(Icorr) & FATT, and the m & C and Icorr.
Ni-Cr-Mo-V강의 전기화학적 방법에 의한 내식성 평가
권재도,문윤배,Kwon, Jae-Do,Moon, Yun-Bae 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.9
When the structures are exposed to their own an application for a long period, a number of variables such as strength properties and corrosion resistance, so on are expected to change. In the present investigation the corrosion behavior and resistance for the original and degraded materials of Ni-Cr-Mo-V steel were evaluated under the conditions of pH 3, 6, 9 and 12 in a distilled water environment. The electrochemical polarization technique was employed in this investigation. Based upon the experimental results obtained, the following conclusions were drawn. A severe and uniform corrosion was observed for both original and degraded materials under the condition of pH 3. At pH 6 and pH 9, these materials showed the degradation by a pitting corrosion. The materials under pH 12 environment were degraded by a uniform corrosion. The corrosion rate per year were the highest in the pH 3 environment, followed by pH 12, pH 6 and pH 9 environment in order. The corrosion resistance was decreased from the original material, slow cooled material (10.deg. C/hr) and step cooled material in order.
SiC 입자 보강 AI 복합재료의 통계학적 피로균열진전거동에 관한 연구
권재도(Jae-Do Kwon),문윤배(Yun-bae Moon),안정주(Jung-Ju Ahn) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_1
The silicon carbide particles reinforced aluminium 6061(SiCp/ AI composites are generally known have wild range of applications from automobiles to airospaces. But. by the results of existing study for SiCp/AI composites. there are reports that the fatigue life of SiCp/AI composites has improved than Al matrixes and res not improved then AI matrixes.<br/> Consequently. in order to perform the reliable life prediction for SiCp/Al. the properties of probability distribution of fatigue crack initiation life & fracture life. crack growth length in regular number of cycle, crack growth rate in regular stress intensity factor range and m & C value in Paris's fatigue crack growth law and the estimation of statistical parameters have been evaluated by the statistics method
320℃에서의 인코넬 합금의 프레팅 피로 거동 평가에 관한 연구
권재도(Jae-do Kwon),정한규(Han-kyu Jeung),정일섭(IlSup Chung),박대규(Dae-kyu Park),윤동환(Dong-hwan Yoon) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.8
원자력 발전설비의 증기발생기용 세관 재료로 인코넬 합금이 사용되고 있다. 인코넬 합금은 고 니켈과 크롬의 합금으로 고온에서 내부식성이 뛰어난 특성을 가지고 있다. 본 연구에서는 인코넬 600 과 690 합금에 대해 실제 원전의 운전온도, 즉 320℃가 프레팅 피로 거동에 미치는 영향에 대해 연구해 보았다. 그 결과 320℃에서의 단순 피로한도와 프레팅 피로한도가 상온에서의 단순 및 프레팅 피로한도에 비해 다소 저하하는 것을 알 수 있었다. 아울러 하중 반복회수와 마찰력의 변화 특성도 얻었다. 또한 파단면을 전자현미경으로 관찰하여 프레팅 피로기구도 검토해 보았다. 이와 같은 결과는 실제 운전온도에서 프레팅을 받는 증기발생기의 구조건전성 평가에 활용 가능할 것으로 생각된다. Inconel alloys are generally used as steam generator tubes in nuclear power plants. These alloys are highnickel chromium alloys that exhibit excellent resistance to aqueous corrosion. In this paper, the effects of elevated temperatures such as an operating temperature of 320°C on the fretting fatigue behavior of inconel 600 and 690. We observed that the plain and fretting fatigue limits at 320°C were slightly lower than those at room temperature. The frictional forces varied depending on the number of load cycles. After each test, we studied the fretting fatigue mechanisms via SEM observations. These results can be used for structural integrity evaluations at elevated temperatures and for studying fretting damage in steam generator systems.
전단변형률 제어하에서 열화를 고려한 2상 스테인리스강의 저주기 피로특성 평가
권재도(Jae Do Kwon),박중철(Joong Cheul Park) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Monotonic torsional and pure torsional low cycle fatigue test with artificially degradation were<br/> performed on duplex stainless steel(CF8M). CF8M is used in pipes and valves in nuclear reactor<br/> coolant system. The method of artificially degraded is used thermal aging for 3600 hrs at 430℃ and<br/> specimens is thin-walled tubular. In order to inhibition, crack nucleation and growth of specimen inside<br/> was worked electrolytic-polishing. The mechanical properties of monotonic and low cycle fatigue are<br/> increased by effect of material degradation and transition fatigue life is decreased about 60%.
몬테카르로 시뮬레이션에 의한 $SIC_w$/Al 복합재료의 피로수명에측
안정주,권재도,김상태,Ahn, Jeong-Ju,Kwon, Jae-Do,Kim, Sang-Tae 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.5
It requires uch time and cost to obtain the fatigue crack growth life and fatigue crack growth path morphlogy from the fatigue crack growth tests. In this study, the Monte-Carlo simulation program was developed to predict the fatigue crack growth lofe and fatigue crack growth path morphology of metal matrix composites. Fatigue crack growth lives of 5%, 10%, 15%, 20%, 25% and 30% $SiC_w$/Al composites were predicted by usign the Monte-Carlo Simulation. And the fatigue crack growth lives of 25% $SiC_w$/Al and Almatrix from Monte-carlo simulation were compared with fatigue life from experiments in order to verify the accuracy of Monte-Carlo Simulation program.
조창희,김상태,권재도,Cho, Chang-Hee,Kim, sang-Tae,Kwon, Jae-Do 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.2
This study reviews the influence function method(IFM) for calculating stress intensity factors (SIFs, K) and modifies it to apply for the estimating the residual fatigue life for the cracked components under complex stress fields. An IFM has been developed to analyze SIFs for surface cracks which are subjectedto nonuniformly distributed stresses. Through elastic superposition, the influence function method properly accounts for redistribution of stress as the crack grows through the component. This influence function is unique to the given geometry and independent of the loading. Some examples have been provided to show the effectiveness of the IFM including the distributions of K in a residual stress field. The significant effect of residual stress upon fatigue crack growth in a welded component has been demonstrated with the IFM.
Ni-Cr-Mo-V강의 템퍼링에 의한 미세구조 변화와 하한계 피로균열진전 특성
신훈,문윤배,김상태,권재도 ( Hoon Shin,Yun Bae Moon,Sang Tae Kim,Jae Do Kwon ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.4
Near-threshold fatigue crack growth characteristics was investigated on the Ni-Cr-Mo-V low alloy steel, which has the different microstructure obtained by tempering at various temperature. The specimens were austenized at 950℃ and then followed by tempering at 200℃, 530℃ and 600℃. Strain rate was obtained from strain gauge attached on the crack tip and crack opening point was observed through load-strain curve. Threshold stress intensity range(ΔK_(th)) was increased with increasing tempering tempuerature, but the effective threshold stress intensity rage(ΔK_(eff.th)) was not affected with the increasing temperature. Grain size increased with increasing tempering temperature.
우창수(Woo Chang-Su),권재도(Kwon Jae-Do) 한국철도학회 1999 한국철도학회 학술발표대회논문집 Vol.- No.-
The axle spring is used in primary suspension component of railway vehicles. The most important factor of axle spring is to have adequate spring constant for comfortable feeling of ride. The non-linear properties of rubber which were important parameter to evaluate of rubber components, were determined by the characteristic test. The finite element analysis of the axle spring are executed to predict the behavior of deformation and stiffness by using commercial FEA code.
최성종(Sung-jong Choi),권재도(Jae-do Kwon),배용탁(Yong-tak Bae) 한국자동차공학회 2003 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The frettingdamage decreases in 50-70 % of the plain fatigue strength. In the present study, the degraded 1Cr-0.5Mo steel used for long period time at high temperature (about 515 oC) and artificially reheat-treated materials are prepared. These materials are used for evaluating an effect of thermal aging on the fretting fatigue behavior. Through the experiment, it is found that the fretting fatigue endurance limit of the reheat-treated 1Cr-0.5Mo steel decreased about<br/> 46 % from the non-fretting fatigue endurance limit, while the fretting fatigue endurance limit of the degraded 1Cr-0.5Mo steel decreased about 53 % from the non-fretting fatigue endurance limit. The maximum value of fatigue endurance limit difference is observed as 57 %(244 MPa) between the fretting fatigue of degraded material and non-fretting fatigue of reheat-treated material.