실배관 파괴특성 평가에 관한 연구(Ⅱ)

박재실(Jae-Sil Park),석창성(Chang-Sung Seok) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5

In order to perform elastic-plastic fracture mechanical analyses, fracture resistance curves for concerned materials are required. The standard CT specimen was used to obtain fracture resistance curves. But the fracture resistance curve by the standard CT specimen was very conservative to evaluate the integrity of the structure. And fracture resistance curve was affected by the specimen geometry and crack plane orientation. The objective of this paper is to be certain the conservativeness of the fracture resistance curve by the standard CT specimen and to provide the additional safety margin. For these, the fracture tests using the real pipe specimen and standard CT specimen test were performed. 4-point bending jig was manufactured for the pipe test and the direct current potential drop method was used to measure the crack extension and the length for the pipe test. From the result of the pipe and the standard CT specimen test, it was observed that the fracture resistance curve of the standard CT specimen test was conservative compare to that of the pipe specimen test.

DCPD법을 이용한 배관 균열 길이 측정에 관한 연구

박재실(Jae-Sil Park),석창성(Chang-Sung Seok) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8

In order to perform elastic-plastic fracture mechanical analyses, fracture resistance curves for concerned materials and real components are required. The unloading compliance method and the DCPD(Direct Current Potential Drop) method have been widely used for measuring the crack length and the extension for the standard specimen fracture resistance curve test. But the unloading compliance method is to be difficult on the real pipe fracture resistance curve test. The objective of this paper is to propose the calibration equation between the normalized crack length and the normalized electric potential, and to adapt to real pipe fracture resistance curve test. For these, finite element analyses were performed with various current input locations and crack front configurations, and the 4-point bending jig was manufactured for the pipe test and the DCPD method was used to measure the crack extension and the length for the pipe test. From the real pipe test results, it was observed that the crack extended to between the circumferential and the longitudinal direction and the modified crack length on the crack extension direction was to agree with test results within 5% errors.

수정된 하중비법을 이용한 배관 시험편의 균열 길이 계산

박재실(Jae Sil Park),석창성(Chang Sung Seok) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

The objective of this paper is to apply the load ratio method for the measurement of the crack length for the real scale pipe specimen. The load ratio method was modified and finite element analyses were performed to derive the equation between normalized compliance and normalized crack length for a pipe specimen. The direct current potential drop method and the load ratio method were used to measure the crack length and extension for a pipe test. The applicability of the proposed load ratio method was confirmed by comparing the calculated crack length with the measured crack length from a pipe experiment.

대차 프레임용 SM490A 용접재의 피로 특성 평가

박재실(Jae Sil Park),석창성(Chang Sung Seok),구재민(Jae Mean Koo),신재호(Jae Ho Shin),구병춘(Byeong Choon Goo) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.12

실배관 시험편의 균열 길이 측정에 관한 연구

박재실(Jae Sil. Park),석창성(Chang Sung. Seok) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

Fracture resistance curves for concerned materials are required in order to perform elastic-plastic<br/> fracture mechanical analyses. Fracture resistance curve is built with J-integral values and crack<br/> extension values. The objective of this paper is to apply the load ratio method to the measurement of<br/> the crack length for the real scale pipe specimen. For these, the fracture test using the real scale pipe<br/> specimen and finite element analyses were performed. A 4-point bending jig was manufactured for the<br/> pipe test and the direct current potential drop method and the load ratio method was used to measure<br/> the crack extension and the length for the real scale pipe test. Finite element analyses about the<br/> compliance of the pipe specimen were executed for applying the load ratio method according to the<br/> crack length.

원전 배관재 다층 용접부의 파괴 특성에 관한 연구

박재실,석창성,Park, Jae-Sil,Seok, Chang-Seong 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.3

The objective of this paper is to evaluate the fracture resistance characteristics of SA508 Cl.1a to SA508 Cl.3 welds manufactured for the reactor coolant loop piping system of nuclear power plants. The effect of the crack plane orientation to the welding process orientation and the preheat temperature on the fracture resistance characteristics were discussed. Results of the fracture resistance test showed that the effect of the crack plane orientation to the welding process orientation of the fracture toughness is significant, while that of preheat temperature on the fracture toughness is negligible. The micro Vickers hardness test, the metallographic observation and the fractography analysis were conducted to analyse the crack jump phenomenon on the L-R crack plane orientation in the multi-pass welding zone. As these results, it is shown that the crack jump phenomenon was produced because of the inhomogeneity between welding beads and the crack plane orientation must be considered for the safety of the welding zone in the piping system.

터빈로터 수명예측 프로그램의 개발 및 민감도 분석

박재실,석창성,서명원,홍경태,Park, Jae-Sil,Seok, Chang-Sung,Suh, Myung-Won,Hong, Kyung-Tae 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.10

Steam turbine rotors are the most critical and highly stressed components of a steam power plant; therefore, the life expectancy of the turbine rotor is an important consideration for the safety of a steam power plant. The objective of this paper is to develop a life estimation program for turbine rotors for all possible operating conditions. For this purpose, finite element analysis was carried out for four normal operating modes (cold, warm, hot and very hot starts) using ABAQUS codes. The results are made into databases to evaluate the life expenditure for an actual operating condition. For any other possible abnormal operating condition, the operating data are transmitted to the server (workstation) through a network to carry out finite element analysis. Damage estimation is carried out by transmitting the finite element analysis results to the personal computer, and then the life expectancy is calculated.

표준 CT시험편을 이용한 실배관 파괴저항 곡선 예측

박홍선(Hong-Sun Park),허용,구재민(Jae-Mean Koo),석창성(Chang-Sung Seok),박재실(Jae-Sil Park),Sung-Keun Cho 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.9

The estimation method of the fracture resistance curve for the pipe specimen was proposed using the load ratio method for the standard specimen. For this, the calculation method of the load - CMOD curve for the pipe specimen with the common format equation(CFE) was proposed by using data of the CT specimen. The proposed method agreed well with experimental data. The J-integral value and the crack extension were calculated from the estimated load - CMOD data. The fracture resistance curve was estimated from the calculated J-integral and the crack extension. From these results, it have been seen that the proposed method is reliable to estimate the J-R curve of the pipe specimen.

정규화법을 이용한 원전배관 용접부의 동하중 파괴저항시험

허용(Yong Huh),조성근(Sung Keun Chop),박재실(Jae Sil Park),석창성(Chang Sung Seok) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

The unloading compliance method is the most commonly used method to evaluate the fracture resistance characteristics of a material. In dynamic loading condition, the direct current potential drop(DCPD) method has been used because the unloading compliance method can not be applied due to the discontinuity of loading. However, even in the dynamic test using DCPD method, there is a problem that the voltage drops sharply on the initiation of crock. For the reason metioned above, the normalization method was suggested on ASTM E 1820 which is revised recently, as a new method to evaluate the dynamic fracture resistance characteristic. The nomalization method can be used to obtain a fracture resistance curve directly from a load-load line displacement. In this study, we obtained two fracture resistance curves from static test of welding part of nuclear piping both by unloading compliance and nomalization method. The two curves were almost some each other, so the adaptability of the nomalizotion method has been proved. We conducted a dynamic fracture resistance test for the some material. The fracture resistance curve from the dynamic test was obtained by normalization method and compared to that of the static test result.

HIPS(HR-1360) 재료의 피로 특성 평가

강민성(Min Sung Kang),구재민(Jae Mean Koo),석창성(Chang Sung Seok),박재실(Jae Sil Park) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.6

최근에는 물류비용의 증가로 인한 경제적 문제 해결과 사용자의 편의성, 효율 증대를 위하여 많은 사무용 기기 및 가전제품의 부품이 고분자 복합재료로 대체되고 있다. 금속 재료와 비교해 볼 때 이러한 고분자 복합재료는 내구 한도가 낮고 환경에 따라 변형이 심하여 사용 횟수의 증가 및 사용 시간의 증가로 인해 피로 파괴 문제가 빈번하게 발생하고 있다. 본 논문에서는 최근 많이 사용되고 있는 HIPS(High Impact Polystyrene, HR-1360) 재료를 대상으로 하여 20℃ (상온), 40℃, 60℃ 환경 조건에서의 정적 강도 특성을 평가하였으며, 피로 시험을 통하여 HIPS 재료의 피로 수명(S-N) 선도를 구하였다. 또한 마이크로 비커스 경도 시험기를 이용한 경도 시험을 통해 인장강도와 내구 한도를 예측해 보았다. In recent times, there has been considerable interest in HIPS (High Impact Polystyrene) materials for their use in construction of office equipments, home electronics, housing for electronics appliances, packing containers, etc. However, these materials suffer from problems caused by fatigue fracture. Further, their strength is substantially affected by environmental conditions. Therefore, in this study, the effect of temperature was analyzed by performing a tensile test and a fatigue test. It was observed that the yield strength, the ultimate strength, and the fatigue life decreased relatively with an increase in temperature. Further, an S-N curve can be predicted by using the results of the tensile test and a micro-Vickers hardness test.