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탄소강, 저합금강의 고온피로크랙 전파하한계 특성에 관한 연구
박경동 釜山工業大學校 1994 論文集 Vol.36 No.-
Fatigue crack growth characteristics and crack closure for Carbon and low alloy steel were investigated at elevated temperature(25℃, 80℃, 100℃, 150℃, 288℃, 350℃). The results obtained are summarized as follows: (1) The occurrence of oxidation of crack surfaces at elevated temperature can affect the formation of fretting oxide debris in fatigue crack growth and has an importan trole on the near-threeshold characteristics. (2) It can be possible to exclude the contribution due to fretting oxide debris and oxidation at elevated temperature on the near-threshold characteristics by the selection of moderated test temperature. In this case, the characteristics are controlled only by plasticity induced crack closure and become a structure-and environment-insensitive material constant.
低合金鋼의 高溫波勞균열進展 下限界特性의 酸化被膜의 效果
朴卿東 釜山工業大學校 1992 論文集 Vol.34 No.-
At elevated temperature which is still below the creep operating region in air or water environment, characteristics of fatigue crack growth threshold for alloy-and carbon-steels are not well clarified. For the structural integrity operating at those temperature ranges, such as nuclear reactors, it is an urgent task to make clear them up. In the previous study, the fatigue crack growth rates and the crack closure were measured for a low alloy steel, JIS SFVV3 (A508-3), used for the pressure vessedl of the nuclear reactor. The temperature range examined was from foom temperature up to 350℃ which covers the operating temperature at 288℃ of the nuclear reactors. Further detailed studies were attempted by accumulating the threshold data for various alloy-and carbon-steels. Influencing factors are made clear and a simple method for predicting thresholds is developed by accounting for the above effects. The temperature dependence on the growth rate and the crack closure and the stress ratio effect are studied. Especially near the fatigue threshold where the temperature effect is significant, it is found that the oxidation produced on the crack surfaces at elevated temperaure have an important role. Their contribution is examined quantitatively. At room temperature, the fretting oxide debris (Fe??O??) cause the crack closure. Higher the temperature, the oxidation(Fe??O??) protects the crack surfaces from the ocurrence of fretting oxide. Thus the fatigue threshold decreases as increasing temperature up to around 100℃. Hereafter, it increases due to the increasing in thickness of oxidation which promotes the occurrence of crack closure. The dependencies of the yield stress and the cyclic frequency on the growth rates can be explained from the same view point.
석유시추용 인코넬 625강의 FCAW 용접에 관한연구 ; 보호가스 변화가 기계적 성질에 미치는 영향
박경동(KEYUNG-DONG PARK),진영범(YOUNG-BEOM JIN),박형동(HYOUNG-DONG PARK) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.6
Inconel 625 is useful in a variety of industrial applications because of the resistance to attack in various corrosive media at temperatures from 200℃ to over 1090℃, in combination with good low and high temperature mechanical strength. Rencently this material has also been widely used in offshore processing piping in order to extend the maintenance term and improve the quality of anti-corrosion. In general, high quality weldings for this material are readily produced by commonly used processes. How, not all processes are applicable to this material group of Ni-alloys. Metallurgical or the unavailability of matching, position or suitable welding processes produce a lower quality. Nowadays, the flux cored wire is developed and applied for increased productivity in several welding positions, including the vertical position. In this study, the weldability and weldment characteristics(mechanical properties) of inconel 625 are considered in FCAW(Flux Core Arc Welding) associated with the several shielding gases(80%Ar+20%CO2, 50%Ar+50CO2, 100CO2) in view of welding productivity.
박경동(Keyung-Dong Park),김동욱(Dong-Woog Kim) 한국마린엔지니어링학회 2005 한국마린엔지니어링학회 학술대회 논문집 Vol.2005 No.-
In this study, it was investigated about endurance and fatigue crack propagation rate of according to welding methods of SMAW and FCAW commonly using for welding structures in present. Endurance limits carried out highly in the order of SMAW, FACW and fatigue crack propagation rate out lowly in the order of SMAW, FCAW. By these results, it is needed to used SMAW welding methods for welding structures with small welding capacity and FACW methods for large welding structures after consideration about economic gains and operation efficiency of welding. Fatigue crack propagation rate is more effected by strength of welding materials than endurance limit of welding materials according to welding methods.
박경동(Keyung-Dong Park),유형주(Hyoung-Ju Ryu) 한국마린엔지니어링학회 2005 한국마린엔지니어링학회 학술대회 논문집 Vol.2005 No.-
The lightness of components required on marine and shipbuilding industry is requiring high strength of components. In particular, fatigue failure phenomena, which happen in metal, bring on danger in human life and property. Therefore, antifatigue failure technology takes an important part of current industries. In this study, it was investigated about endurance and fatigue crack propagation rate of according to stress ratio of SMAW commonly using for welding structures in present. Fatigue crack propagation rate(da/dN) of low load(R=0.1) was lower than of high load(R=0.6) for piping weld. And in stage Ⅰ, △Kth, the threshold stress intensity factor of the weld under heavy load is higher than under small load. Fatigue life shows more improvement in the weld of stress ratio R=0.1 than in the weld of stress ratio R=0.6.
박경동(Keyung-Dong Park),김동욱(Dong-Uk Kim) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
Rupture by corrosion of pipe becomes the factor of supply water's pollution in waterworks and the factor of pollution of the soil and environment in drain pipe. Therefore, this research examined the weight reduction electric potential measure to measure the corrosion degree of piping materials after testing the corrosion of piping materials(Copper Pipe, Galvanized Steel Pipe, Stainless Steel Pipe) which is generally used at the moment in various corrosion environments(subterranean water, supply water, 3.5% NaCl, 3.5% HNO₃, 1% H₂SO₄). And let me show basic design data about problem occurrence such as leakage water, rust water, inside and outside corrosion from this.
반복하중을 받는 배관용 강재의 피로수명에 미치는 부식의 영향
박경동(Keyung-Dong Park),안재필(Jae-Pil An) 한국마린엔지니어링학회 2005 한국마린엔지니어링학회 학술대회 논문집 Vol.2005 No.-
The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, it was not known that the effect of shot peening in corrosion environment. In this study, the effect of shot peening on corrosion fatigue crack growth of sping steel immersed in 6% FeCl₃ solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of spring steel are as follows; the fatigue crack growth rate of the shot peening material was lower than of the un peening material. And fatigue life shows more improvement in the shot peening material than un peening material. This is because the compressive residual stress of surface operate resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.
김동욱(Dong-Woog Kim),박경동(Keyung-Dong Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Antifatigue failure technology take an important the part of current industries. Currently, the shot peening is used for removing the defect from the surface of steel and improving the fatigue strength on surface. In this study, the influence of shot peening and corrosive condition for corrosion property was investigated on immersed in 3.5% NaCl, 10% HNO3 + 3% HF, 6% FeCl3. The immersion test was performed on two kind of specimen. The immersion periods was performed 30days, 90days. Corrosion potential, weight loss were investigated from experimental results.