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석창성,전남규,박재형,김기근,박기범 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.2
Fatigue life evaluation of mechanical parts is important for product safety. Fatigue life evaluation using S–N diagrams is important for mechanical parts at risk of fatigue failure owing to periodic tensile stress. Automobile engine valves are at risk of fatigue failure owing to high temperatures and repeated tensile stress inside the engine. In particular, cases of field failure in weak areas owing to the structural characteristics of the stem end have been reported. Therefore, a test device should be developed for conducting research to improve the fatigue life of engine valves by accurately evaluating the fatigue life of the stem end of engine valves. In this study, the actual condition and structural characteristics of the stem end of engine valves were analyzed, and a device for evaluating its fatigue life was developed. In addition, the performance of the developed test device was verified through a dynamic motion relationship analysis and finite element analysis. The reliability and utility of the device were verified by deriving an S–N diagram through the fatigue test.
재료의 탄소성 파괴인성치 $J_{IC}$의 온도 의존성에 관한 연구 I - AST과 JSME의 $J_{IC}$ 시험법에 관한 비교연구 -
석창성,최용식,양원호,김영진 대한기계학회 1989 대한기계학회논문집 Vol.13 No.4
본 연구에서는 실험방법과 해석방법 등의 차이가 J$_{IC}$ 값에 미치는 영향을 고찰하여 보았으며, E 813-81법으로 해석된 J$_{IC}$ 값으로 환산하는 방법을 제안하고 몇 가지 재료와 환경에서 그 오차를 검토하였다.하였다. Elastic-plastic fracture toughness J$_{IC}$ can be used as an effective design criterion in elastic plastic fracture mechanics. In the J$_{IC}$ test methods approved by ASTM and JSME, there are discrepancies such as the definition of J$_{IC}$, the slope of the blunting line, curve fitting method and the measurement of crack extension etc. The objective of this paper is to evaluate the effect of these discrepancies on the determination of J$_{IC}$ values. Fracture toughness tests were performed on A516, SA508 and SCM415 steels, and test results were analyzed according to ASTM E 813-81, ASTM E 813-87 and JSME S 001-1981. Results showed significant differences depending on the analysis methods. Therefore, a conversion equation between two ASTM methods was proposed, and the conversion error was within acceptable range(less then 8.5%)en 8.5%)
울진 원자력 발전소 3 , 4 호기 1 차계통 배관소재의 파괴저항특성 평가
석창성,김수용,강병구,박재실,윤병곤 한국산업안전학회 1999 한국안전학회지 Vol.14 No.1
The objective of this paper is to evaluate the fracture resistance characteristics of SA508 CL.la carbon steel, TP347 stainless steel and their associated welds manufactured for primary coolant system of Ulchin 3,4 nuclear power plants. The effect of various parameters such as pipe size, welding method, chemical composition, crack plane orientation, metallography and fractography on the material properties were discussed. Test results showed that the effect of pipe size on fracture toughness is negligible while the effect of welding method on fracture toughness is significant. In addition, the drop of fracture toughness in the field fabrication weld of TP347 stainless steel is probably due to the large amount of σ-phase precipitated on the δ-ferrite boundary and the large size dimples.
석창성,김정표,송성진,김훈모,김재원,김수용,Seok, Chang-Seong,Kim, Jeong-Pyo,Song, Seong-Jin,Kim, Hun-Mo,Kim, Jae-Won,Kim, Su-Yong 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.12
The BI(Ball Indentation) method has a potential to assess the mechanical properties and to replace conventional fracture tests. In this study, the BI test system has been developed to evaluate material properties. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed by the system using four classes of thermally aged specimens. The results of the BI tests were in good agreement with fracture characteristics from a standard fracture test method.
석창성,김동중,배봉국,Seok, Chang-Seong,Kim, Dong-Jung,Bae, Bong-Guk 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.12
The remaining life estimation for the aged components in power plants as well as chemical plants are very important beacuse mechanical properties of the components are degraded with time of service exposure in high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components nondestructive techniques are needed to estimate the degradation. In this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at 630$\^{C}$. And the DC potential drop method and destructive methods such as tensile, K(sub)IC and hardness tests were used in order to evaluate the degradation of 1-Cr-1Mo-0.25V steels. The objective of this study is to investigate the possibility of the application of DCPD method to estimated the material degradation, and to analyse the relationship between the electrical relationship between the electrical resistivity and the degree material degradation.
석창성,김수용,Seok, Chang-Seong,Kim, Su-Yong 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.12
In order to obtain more realistic fracture resistance curve, research is currently underway to introduce new parameter and to quantify the constraint effect. The objective of this study is to investigate the relationship between the constraint effect of a size(plane size and thickness) and the fracture resistance curve. In this paper fracture toughness tests were performed with various plane size and various thickness of specimens in two materials. The test results showed that the effects of plane size in th4 J-R curve were significant and the curve was risen with an increase in plane size. However, relatively weak influence was observed form the change of the specimen thickness and size. The stress fields near the crack tip of th specimen is close to the HRR field according to increasing the plane size and Q stress appears different value according to material properties and the plane size.