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한계하중법을 이용한 Curved CT 시험편의 파괴저항곡선에 미치는 형상변수 영향 평가
신인환(In Hwan Shin),박치용(Chi Yong Park),석창성(Chang Sung Seok),구재민(Jae Mean Koo) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.7
본 연구에서는 한계하중법을 이용하여 Curved CT 시험편의 J-적분에 미치는 형상변수 영향을 평가하였다. 주요 형상변수인 시험편의 길이와 폭의 비(L/W), 평균곡률반경과 두께의 비(Rm/t)에 대한 파괴인성시험 후, ASTM 시험법에서 제시한 표준시험편의 J-적분과 한계하중법으로 구한 J-적분을 각각 적용하여 구한 파괴저항곡선을 평가하였다. 또한 배관의 파괴저항곡선을 잘 모사한다고 알려진 휨 광폭평판(CWP) 및 표준시험편의 파괴저항곡선과 비교? 고찰하여 최종적으로 Curved CT 시험편의 파괴저항곡선에 대한 유효성을 평가하였다. 본 논문의 결과는 향후 실배관의 정확한 파괴인성을 평가하는 데 있어 Curved CT 시험편의 적용가능성을 평가하는 데에 활용할 수 있다. In this study, the effect of shape parameters on the J-R curves of curved CT specimens was evaluated using the limit load method. Fracture toughness tests considering the shape factors L/W and Rm/t of the specimens were also performed. Thereafter, the J-R curves of the curved CT specimens were compared using the J-integral equation proposed in the ASTM (American Society for Testing and Materials) and limit load solution. The J-R curves of the curved CT specimens were also compared with those of the CWP (curved wide plate), which is regarded to be similar to real pipe and standard specimens. Finally, the effectiveness of the J-R curve of each curved CT specimen was evaluated. The results of this study can be used for assessing the applicability of curved CT specimens in the accurate evaluation of the fracture toughness of real pipes.
임만배(MAN-BAE LIM),차귀준(GEE-JUN CHA),윤한기(HAN-KI YOON),공유식(YU-SIK KONG),김정호(JUNG-HO KIM) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.3
SG-365 steel is an important material and used for manufacturing a pressure vessel which the gas piping. In this investigation, the elastic plastic fracture toughness of this material is evaluated by the an unloading compliance method according to the ASTM E813-97 and E1152-97 method on the smooth and side groove 1CT specimens. The effect of smooth and side groove is studied on the elastic plastic fracture toughness. The side grooved specimen is very useful in estimation of the JIC. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method Besides, it improves the accuracy of toughness values, decreases the scattering of them and tunneling and shear lip by the side groove.
SA508-3재의 제하컴플라이언스법과 하중비해석을 이용한 파괴저항곡선 평가
임만배(Man-Bae Lim),차귀준(Gee-Jun Cha),윤한기(Han-Ki Yoon),안원기(Won-Ki An) 한국해양공학회 1998 韓國海洋工學會誌 Vol.12 No.1
The fracture resistance curve is one of most important and design techniques employed in nuclear pressure vessel structures. This study is to evaluate the J-R curve characteristics for the SA508C-3 by the unloading compliance method and load ratio analysis. The effect of strain aging for the exponential correlation of the J-R curve in this metal are investigated at room temperature, 200℃ and 300℃. The load ratio analysis method can evaluate the J-R curve by using the simple tension load-displacement curve only without the repeat of the unloading and loading. Therefore, the analysis by the proposed load ratio method has a merit, in comparison with the unloading compliance method, which can measure the crack length without the precision measurement equipment.
오스테나이트계 스테인리스강 용접재(ER347)의 파괴인성에 미치는 열화 영향 평가
신인환(In Hwan Shin),이호중(Ho Jung Lee),박상규(Sang Kyu Park) 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.3
본 연구에서는 ER347 용접재의 파괴인성에 미치는 열화 영향을 평가하기 위하여 GTAW 방식으로 덧살올림 용접한 블록에 대한 인장 및 파괴인성시험을 수행하였다. 열화 후 ER347 용접부의 강도가 열화 전에 비해 약 10 % 증가하였으나 5,000 시간 이후에는 강도 변화가 둔화되었다. 그러나 파괴인성은 열화시간에 반비례하여 꾸준히 감소하였다. 시험결과를 토대로 볼 때 ER347 용접재의 열화 영향을 정확히 평가하기 위해서는 강도 뿐 만 아니라 파괴인성도 함께 고려해야 할 것으로 보인다. 또한 ER347 용접재의 파괴인성이 주조스테인리스강, E308 및 ER316 용접재에 비해 상대적으로 높게 나타났는데 이에 대한 원인은 델타-페라이트의 함량, Nb 성분으로 보이며 이에 관한 후속 연구를 수행할 예정이다. In this study, we evaluated the thermal aging effect of ER347 welds by performing tensile and fracture toughness tests for welding blocks made by GTAW and the build-up welding method. The strength of the aged welds increased by approximately 10% compared to that of the as-welded status, and the variation in strength slowed after 5,000 hours. However, the fracture toughness of welds decreased gradually in inverse proportion over time. The test results suggest that fracture toughness, as well as strength, should be considered to accurately evaluate the thermal aging effect. Furthermore, the fracture toughness of ER347 welds was determined to be higher than that of cast stainless steel, E308 and ER316 welds. This may be occurring due to the δ-ferrite contents and Nb component. A follow-up study will be conducted on this issue.
수정된 하중비법을 이용한 배관 시험편의 균열 길이 계산
최정훈(Jung-Hun Choi),구재민(Jae-Mean Koo),석창성(Chang-Sung Seok),허용(Yong Huh),박재실(Jae-Sil Park) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.12
The objective of this paper is to apply the load ratio method to the measurement of the crack length of the real scale pipe specimen. The load ratio method was modified and finite element analyses were performed to derive the relationship between the normalized compliance and the normalized crack length for the pipe specimen. In order to measure the crack length, the direct current potential drop method and the modified load ratio method were applied to the pipe test. The applicability of the modified load ratio method was confirmed by comparing the calculated crack length with the measured crack length from the pipe experiment.
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.
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.