• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.96-104
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• 1989

The behaviors of acoustic emission emitted in the tests of the fracture toughness and fracture stability are observed by using the specimens of aluminum 2024-T351 and 7039-T6 alloys. The empirical eqution of J-R curve is derived. It is demonstrated from the comparison of the fracture toughness obtained from J-R curve with that from ASTM standard E813-81 that the latter is larger than the former. The discontinuous point in the log-log graph of J-integral vs. total acoustic emission count is observed in between the two offset lines referred from ASTM standard E813-81, but it's physical meaning is uncretain. An empirical material tearing modulus is derived in terms of the total acoustic emission count and proved to be valid in fracture instability test.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.65-75
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• 1998

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 rato analysis. The effect of strain aging for the exponential correlation of the J-R curve in this metal are investigated at room temperature, 20$0^{\circ}C$ and 30$0^{\circ}C$. 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1051-1061
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• 1995

In order perform leak-before-break design of nuclear piping systems and integrity evaluation of reactor vessels, full stress-strain (.sigma. - .epsilon.) curves and fracture resistance (J-R) curves are required. However it is time-consuming and expensive to obtain J-R curves experimentally. The objective of this paper is to develop two methods for J-R curve prediction. In the first method, elastic-plastic finite element analyses for a series of crack length / specimen width ratio were performed. Accordingly the load versus load line displacement (P .delta.) curve corresponding to the fracture strain is obtained and the J-R curve based on the generalized locus method is obtained. In the second method, the correlation between .sigma.-.epsilon. curves and J-R curves was statistically analyzed and an empirical equation to predict the J-R curve from the .sigma.-.epsilon. test result is proposed. A good correlation between the predicted results based on the proposed methods and the experimental ones is obtained.

• Journal of Ocean Engineering and Technology
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• v.1 no.1
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• pp.94-103
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• 1987

균열불안정 해석법인 COD설계곡선법과 R6파괴 평가도법에 있어서 그 응용 한계의 확립과 타당성 수준의 정량화를 위해 포괄적인 비교 연구가 수행되었다. 참고로서 J-적분 균열불안정성 해석법이 이용되었다. 본 연구의 결과로서, 균열확장의 유무에 대한 R6 파괴 평가도법이 매우 우수한 방법임을 보여준다. COD 설계곡선법에 대한 영국 표준국 순서에 따른 결과로서는, 큰 스캐터 밴드를 가진 상당량의 부당성 해를 보여준다. 이러한 COD설계곡선법의 해를 개선하기 위한 새로운 접근법이 개발되었고, 그 타당성이 입증되었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1796-1808
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• 1997

In order to perform leak-before-break design of nuclear piping systems and integrity evaluation of reactor vessels, full stress-strain curves and fracture resistance(J-R) curves are required. However it is time-consuming and expensive to obtain J-R curves experimentally. To resolve these problems, three different methods for predicting J-R curves from tensile data were proposed by the authors previously. The objective of this paper is to develop a computer program based on those J-R curve prediction methods. The program consists of two major parts ; the main program part for the J-R curve prediction and the database part. Several case studies were performed to verify the program, and it was shown that the predicted results were, in general, in good agreement with the experimental ones.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1786-1795
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• 1997

In order to perform leak-before-break design of nuclear piping systems and integrity evaluation of reactor vessels, full stress-strain curves and fracture resistance (J-R) curves are required. However it is time-consuming and expensive to obtain J-R curves experimentally. The objective of this paper is to modify two J-R curve prediction methods previously proposed by the authors and to propose an additional J-R curve prediction method for nuclear piping materials. In the first method which is based on the elastic-plastic finite element analysis, a blunting region handling procedure is added to the existing method. In the second method which is based on the empirical equation, a revised general equation is proposed to apply to both carbon steel and stainless steel. Finally, in the third method, both full stress-strain curve and finite element analysis results are used for J-R curve prediction. A good agreement between the predicted results based on the proposed methods and the experimental ones is obtained.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.79-86
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• 1990

A method to determine directly $J_{IC}$ from load-displacement curve without measuring crack growth amount is studied. A method to use key curve in determination of $J_{IC}$ is also considered. The values of $J_{IC}$ obtained from the above methods are compared with that obtained from the ASTM standard test method (E813). By performing experiments using both compact-tension specimen and three-point-bending specimen of a structural alloy steel SCM4, it is shown that the methods proposed here may be used in determination of $J_{IC}$.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.127-133
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• 2007

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 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 $J_{IC}$. 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 a phenomenon of the tunneling and shear lip by the side groove.

• Journal of the Korean Society of Safety
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• v.12 no.3
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• pp.45-51
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• 1997

To evaluate the elastic-plastic fracture toughness by this modified offset method, the origin of J-R curve is set with drawing the blunting line on the maximum point of the negative crack growth and R curve is modified by adding the blunting factor of the experimented point on the R curve. The elastic-plastic fracture toughness $J_{IC]$ of A5083-H112 material by the modified offset method we 44kN/m on the smooth CT specimens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.794-802
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• 2000

Since the examination of CTOD problem revealed that the discrepancy among CTOD's was a matte., of definition, the relationships among parameters based on different definitions have been studied Particularly, the relationship between $\sigma$BS R-curve based on BS 7448 and R-curve based on the recently introduced $\sigma$5 parameter was investigated in this research. For the comparison, compact tension specimens of used 1Cr-0.5Mo steel, heat treated 1Cr-0.5Mo steel to mimic the new one, A12024-T6, and A12024-T351 were prepared and tested. Consequently, the relationship between $\sigma$5 and $\sigma$BS R-curves for tested materials were established by shifting the rotational center which could determined by rotation factor and ligament size.