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김수용,석창성 기계기술연구소 1999 성균관대학교 논문집 기계기술편 Vol.1 No.1
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 planfrom size and the fracture resistance curve. In this paper fracture toughness tests were performed with various planform size in two materials. The J-R curve is increased with an increase in planform size. And the !-parameter is near the HRR field according to increasing the planform size. But the Q stress appears different value according to material properties.
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.
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.
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.
석창성,임창현,김정표 한국산업안전학회 2001 한국안전학회지 Vol.16 No.2
In the case of a crack propagation, a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile tests were carried out using thermocouples to monitor the variation of temperature. The experimental results show that the temperature of specimen was increased 5.4℃ at static load edition. And the thermal effect is investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip is lower about 16.9% than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.