• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.192-197
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• 2001

To obtain $A_2$ experimentally in the $J-A_2$ theory, deformation field on the lateral surface of a CT specimen was to be determined using Laser speckle method. The crack growth was measured using direct current potential drop method and most procedure of experimental and data reduction was performed according to ASTM Standard E1737-96. Laser speckle images during crack propagation were monitored by two CCD cameras to cancel the effect of rotation and translation of the specimen. An algorithm to pursue displacement of a point from each image was developed and successfully used to measure $A_2$ continuously as the crack tip was propagated. The effects of specimen thickness on J-R curve and $A_2$ were explored.

• 대한기계학회논문집A
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• 제33권9호
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• pp.930-937
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• 2009

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.

• 대한기계학회논문집A
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• 제24권12호
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• pp.3010-3017
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• 2000

For integrity evaluation of cracked or damaged structures, fracture toughness test results in ASTM are widely used. The fracture toughness values of the structures are used as an effective design criterion in nuclear plants and aircraft structures. Sometimes the difference of P-$\delta$ curve trend during the unloading /reloading cycle in the fracture toughness test using partial unloading compliance was observed. The phenomenon as a possible source of error in determining fracture toughness may be caused by the residual stress during unloading work-hardening and bucking of a specimen. Therefore, we evaluate the effect of bucking and compressive residual stress during the K-R and J-R testing using a finite element method.

• 대한기계학회논문집
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• 제10권5호
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• pp.680-688
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• 1986

본 연구에서는 마르텐사이트-페라이트 복합조직강의 파괴인성평가법을 확립하 기 위하여 불균질의 대표적 인자인 페라이트 결정입경 및 마르텐사이트의 강도를 변화 시켜 R곡선법과 SZ법에 의해 파괴인성을 평가하고, SZ법에 의한 $J_{IC}$ 의 과대평가 정 도와 이에 대한 원인을 규명하기 위하여 균열선단의 미시파괴거동을 검토하였다.

• 한국해양공학회지
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• 제7권2호
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• pp.91-102
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• 1993

The elastic-plastic fracture thoughness J sub(IC) of Nuclear Reactor Vessel Steel(SA 508-3) which has high toughness was discussed at temperatures RT, $-20^{\circ}C$, $200^{\circ}C$ and 1/2/CT specimen was used for this study. Especially the two methods recommended in ASTM and JSME were compared. It was difficult to find J sub(IC) by ASTM R-curve method with the specimen used for this research, while JSME R-curve method yielded good result. The stretched zone width menthod gave slightly larger J sub(IC) values than those by the R-curve method for SA 508-3 steel.

• 한국해양공학회지
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• 제9권1호
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• pp.111-119
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• 1995

The elastic-plastic fracture toughness($J_{IC}$) and fracture resistance (J-R curve) of SA508-3 alloy steel used for nuclear reactor pressure vessel are investigated by using CT-type specimens. Fracture toughness tests are conducted by unloading compliance method and multiple specimen method at room temperature, -2$0^{\circ}C$ and 20$0^{\circ}C$. The apparent negative crack growth phenomenon which usually arises in partial unloading compliance test is well known. The negative crack growth phenomenon in determining J sub(IC) or J-R cure from partial unloading compliance experiments may be eliminated by the offset technique. In this study, the evaluation of $J_{IC}$ multiple specimen method recommended by the JSME gives the most reliable results by using half-size CT(similar-type) specimens.

• 대한기계학회논문집A
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• 제24권12호
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• pp.2963-2971
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• 2000

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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1240-1245
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• 2003

Reduced activation ferritic steel (JLF-1) is considered as a promising candidate material for blanket or first-wall structure of D-T fusion reactors. The fracture tests of fracture resistance curve (J-R curve) and $J_{IC}$ are desirable to investigate the exact fracture toughness of JLF-1 steel, since it has a high ductility. The fracture toughness of JLF-1 steel is affected by the configuration of test specimen such side groove, specimen thickness or specimen size. In this study, the fracture toughness tests were performed with various size(plane size and thickness) and various side groove of specimens. The test results showed the standard specimen with the side groove of 40 % represented a valid fracture toughness. The fracture resistance curve increased with increasing plane size and decreased with increasing thickness. However, the fracture resistance curve of half size specimen was similar to that of the standard specimen.

• 한국해양공학회지
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• 제14권1호
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• pp.44-51
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• 2000

Safety and integrity are required for reactor pressure vessels because they are operated in high temperature. There are single specimen method multiple specimen method and load ratio analysis method which used as evaluation of safety and integrity for reactor pressure vessels. In this study the fracture resistance curve(J-R curve) elastic-plastic fracture toughness($J_{IC}$) and material tearing modulus ($T_{mat}$) of SA 508 class 3 alloy steel used as reactor pressure vessel steel are measured and evaluated at room temperature 20$0^{\circ}C$ and 30$0^{\circ}C$ according to unloading compliance method and load ration analysis method. And then the comparison with experimental $J_{IC}$ and theoretical$J_{IC}$ by local fracture strain is managed.

• 한국해양공학회지
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• 제8권2호
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• pp.157-165
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• 1994

Effect of an accelerated iso-thermal aging (375 degree C x 66days, 375 degree C x 200days) on elastic-plastic fracture resistance curve were examined in SA533B low alloy steel. Fracture toughness test are conducted by unloading compliance method at room temperature. But the apparent negative crack growth phenomenon, usually arise in partial unloading compliance test. The phenomenon of negative crack growth may be eliminated by the offset technique. There is no effect of aging on J sub(IC) and dJ/da in iso-thermal aged (375 degree C x 66 days) specimen, but there is very little effect in iso-thermal aged (375 degree C x 200 days) specimen.