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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,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.
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,최용식 대한기계학회 1992 대한기계학회논문집 Vol.16 No.6
본 연구에서는 ASTM의 단일시편법으로 시험해석할 때에 나타나는 가장 큰 문 제점인 균열길이 감소현상의 원인해석과, 균열길이 감소현상을 고려한 균열길이 측정 수정식을 제안하고자 하며, 다음 절차로 연구를 수행하였다. (1) 균열선단의 응력장해석과, 이 응력장해석에 의한 균열길이 감소현상을 해석하였 다. (2) CT와 TPB 시편에서의 균열길이 측정식의 수정식을 제안하였다. (3) 이 수정식의 타당성을 $J_{IC}$ 시험해석을 통하여 검토하였다.다. The apparent negative crack growth phenomenon which usually arises in partial unloading compliance test is well known. The reason for apparent negative crack growth is the compressive residual stress caused by the plastic zone around the crack tip. The phenomenon as a possible source of error in determining $J_{JC}$ or J-R curve from partial unloading compliance experiments may be eliminated by the correction of compliance. A compliance correction equation is derived from a stress field analysis near the crack tip.
J-R 곡선에서의 균열길이 감소현상에 관한 연구 (II)
석창성,최용식 대한기계학회 1992 대한기계학회논문집 Vol.16 No.9
본 연구에서는 균열길이 감소현상의 처리법에 대하여 고찰하고자 하며, 내용 을 요약하면 다음과 같다. (1) 오프세트(offset)법의 배경 및 오프세트법에 의한 균열길이 감소현상의 처리 방법 을 제안하였다. (2) 실제의 균열길이의 측정과 $J_{IC}$실험해석을 통하여, 수정식과 오프세트법의 타 당성을 검토하였다. It often occurs in J-R testing that some initial crack extension (.DELTA.a) data points have anomalous negative values. The reason for the apparent negative crack growth is due to the analysis method. The phenomenon as a possible source of error in determining $J_{IC}$ or J-R curve from partial unloading compliance experiments may be eliminated by the compliance correction equation or the offset technique. In this study, the correction methods are suggested and examined by the measurement of the actual crack length and $J_{JC}$ analysis.
SA508 CL.1a 탄소강 배관소재의 파괴저항특성 평가
석창성,강병구,Seok, Chang-Sung,Kang, Byoung-Gu 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.7
The objective of this paper is to evaluate the fracture resistance characteristics of SA508 CL.1a carbon steel, and their associated welds manufactured for primary coolant piping system of nuclear power plants. The effect of various parameters such as pipe size, welding method and chemical composition on the material properties were discussed. Test results showed that the offset of pipe size on tincture toughness was negligible, while the effect of welding method on fracture toughness was significant. In addition, Fracture toughness for carbon steel was influenced by silicon contents due to the different steel refining processes.